Post-separation Care Arrangements and Parents’ Life Satisfaction: Can the Quality of Co-parenting and Frequency of Interparental Conflict Explain the Relationship?

Although growing numbers of parents share the physical custody of their children after family dissolution, empirical studies on the mechanisms through which post-separation care arrangements may affect parental well-being remain scarce. To fill this lacuna, the present study not only investigated the relationship between post-separation care arrangements and the life satisfaction of resident parents, but also whether the quality of co-parenting and the frequency of interparental conflict—two stressors associated with family dissolution—could explain this relationship. Based on data from the Family Models in Germany (FAMOD) study, structural equation models were estimated for an analytical sample of 1104 resident parents practicing either sole physical custody (SPC) or joint physical custody (JPC). The findings showed that parents with JPC experienced, on average, more life satisfaction than their counterparts with SPC. However, after considering the quality of co-parenting and the frequency of interparental conflict, the study found that the direct relationship between post-separation care arrangements and life satisfaction was no longer significant. Instead, practicing JPC was significantly related to both better co-parenting and fewer interparental conflicts, while the latter two factors were positively related to life satisfaction. In sum, this study showed that framework conditions, specifically elements of the interparental relationship, are more important factors to consider when investigating parents’ post-separation well-being than the type of care arrangement practiced. However, the role of selection processes in explaining these associations remains uncertain, including the question of whether practicing JPC actually enhances the quality of the interparental relationship.


Introduction
Separation and divorce are stressful processes that are usually associated with a deterioration in the well-being of parents (Amato, 2000;Leopold & Kalmijn, 2016;Williams & Dunne-Bryant, 2006). However, family dissolution does not have the same effects on all parents because the severity and duration of its negative effects depend on an interplay of numerous stressors and protective factors. For resident parents, for example, it has been suggested that having sole parenting responsibility is a significant stressor that decreases the quality of parental well-being (Amato, 2010). In post-separation families with minor children, the division of physical custody is a defining feature of family life. Parents (or, in some cases, family courts) have to decide how to allocate the time their children will spend with each of them. Although there are no universally agreed-upon definitions of post-separation care arrangements, sole physical custody (SPC) is understood as an arrangement in which children live either most of the time or the whole time with one resident parent (usually the mother) and have limited or no contact with their non-resident parent (usually the father). Living in a joint physical custody (JPC) arrangement, by contrast, implies that children continue to have meaningful contact with both parents after family dissolution (Bauserman, 2002). In most studies, the threshold for JPC is met when children spend at least 30% of their time with their non-resident parent and live alternately in each parent's household (Steinbach, 2019).
Despite the observation that a growing number of parents share physical custody of their children equally or almost equally after family dissolution (Bergström et al., 2019;Sodermans et al., 2015), research on parental well-being in different types of post-separation families is only just beginning to develop, and very few studies have explored the mechanisms through which care arrangements may affect parental well-being. One reason is that researchers have focused primarily on the relationship between post-separation care arrangements and the well-being of children, given that "the interest in the child is primordial in most divorce legislations" (Sodermans et al., 2015, p. 258). Investigating the post-separation well-being of parents in JPC families is, nevertheless, of great importance, because parental well-being has far-reaching implications not only for the parents themselves, but also for the development of their children (Nomaguchi & Milkie, 2020).
Given the gaps in the literature on the topic of JPC, the central goal of this study was to contribute to the growing body of research in this area by investigating the link between post-separation care arrangements and the life satisfaction of resident parents, considered as a dimension of their subjective well-being. Data from the Family Models in Germany (FAMOD) study were used in analyses of 1104 resident mothers and fathers who practiced either SPC or JPC. An additional aim was to shed light on the mechanisms that underlie a potential association between post-separation care arrangements and parental life satisfaction. A major challenge for separating parents is that they have to adjust to new roles, relationships, and expectations. One particularly important consequence of family dissolution is that adults with minor children have to work out how to maintain their relationship as parents even though their relationship as a couple has ended (Vrolijk & Keizer, 2021). However, at the time of writing, only one study has explicitly examined how post-separation care arrangements are indirectly related to parental well-being through the quality of family relationships . Because the study in question focused on the role of the parent-child relationship, our knowledge of the explanatory power of the interparental relationship remains severely limited. Therefore, the present study considers two crucial indicators of the interparental relationship when examining the link between post-separation care arrangements and parental life satisfaction: the quality of co-parenting and the frequency of interparental conflict. In so doing, this study seeks to answer two research questions: first, whether practicing JPC is associated with parental life satisfaction; and second, whether the quality of co-parenting and the frequency of interparental conflict explain a potential association.

Joint Physical Custody in Germany
Although divorce rates in most Western countries have declined overall in recent years, they have typically stagnated at high levels Raley & Sweeney, 2020). The same pattern can be observed in Germany, where divorce rates are currently high, and approximately one third of married couples get divorced (Wagner, 2019). Half of these divorces involve minor children (Geisler et al., 2018), and post-separation families account for 30% of all families with minor children in Germany (Steinbach et al., 2016). Whereas the numbers of JPC families are already high in Northern European countries such as Sweden and Norway, where 30% to 40% of post-separation families practice this care arrangement (Fransson et al., 2018;Kitterød & Wiik, 2017), the prevalence of JPC is still low in Germany. One study has estimated that only between 4 and 5% of all postseparation families in Germany have a JPC arrangement (i.e., an arrangement in which a child spends at least 40% of nights with each parent; Walper et al., 2021). Other sources suggest that 5% of separated or divorced parents practice asymmetric JPC, while another 4% practice symmetric JPC (i.e., an arrangement that falls between a 50:50 and 60:40 division; Geisler et al., 2018). The percentage of families practicing symmetric JPC was corroborated by other research that showed that 3.6% of parents share physical custody of their children equally or almost equally after family dissolution (Steinbach et al., 2021).
To explain the low prevalence of JPC in Germany, the country's legal framework needs to be considered. Since legislative changes in 1997, parents-both married and unmarried-have a duty of and a right to contact with their minor children. Correspondingly, it was emphasized that minor children have a right to contact with both their parents. Hence, joint legal custody has become the default when parents separate or divorce, giving non-resident parents the opportunity to remain involved in making important decisions about their child, for example decisions about medical treatments that go beyond routine treatments (Geisler et al., 2018). However, while joint legal custody is the norm in Germany, SPC remains the default when parents go to court over the physical custody of their children.
Unlike legislators in other Western countries, the German government has not passed any laws or adopted any policies that would encourage parents to opt for JPC or courts to order families to practice JPC (Steinbach & Helms, 2020). In addition, for a court to order parents to practice JPC it must usually be demonstrated that this care arrangement is in the best interest of the child; that is, it must be shown that JPC is more advantageous for the child than SPC (Helms & Schneider, 2020). The lack of institutional support for JPC is also reflected in regulations concerning child support. The German legal system uses a rather restrictive definition of JPC under which, in most cases, a care arrangement is only recognized as JPC if the parents have a 50:50 division. As a result, family courts may order the non-resident parent in an asymmetric JPC family to pay the same amount of child support as it would if the family had SPC. Although it is more likely that family courts will 1 3 adjust the amount of child support if a family practices symmetric JPC, child support payments may not be abolished completely even in these cases (Schneider, 2021).

Joint Physical Custody and Resident Parents' Well-Being
The central arguments for a positive relationship between JPC and resident parents' wellbeing refer to the advantages that result from sharing parenting responsibilities more equally with the other parent after separation. Children in a JPC family spend up to half of their time with the other parent; hence, resident parents in these families should be at a significantly lower risk of being overburdened by the demands of having sole responsibility for childrearing. Consequently, they should also experience lower levels of stress and fewer time constraints than resident parents in a SPC arrangement (Bernardi et al., 2018;van der Heijden et al., 2016). Previous research has confirmed this by showing that mothers with JPC experienced lower levels of time pressure than mothers with SPC. Fathers with JPC faced more time constraints than their non-resident counterparts, supporting the idea that care demands increase with the time parents spend with their children (van der Heijden et al., 2016). Moreover, a study that used an indicator consisting of psychological distress, parental stress, and subjective economic deprivation to measure maternal well-being demonstrated that mothers with JPC were more likely to experience low levels of strain and less likely to experience high levels of strain than those with SPC (Recksiedler et al., 2022).
Given that separation and divorce have been linked to a decline in economic well-being (Mortelmans, 2020) and social contact (Kalmijn & van Groenou, 2005), practicing JPC should also improve the well-being of resident parents because sharing physical custody equally or almost equally with the other parent allows for more time to invest in other life domains, such as paid employment, leisure activities, and personal relationships. In line with these assumptions, studies have demonstrated that for mothers, practicing JPC was associated with fewer problems in combining paid employment and child care (Bakker & Karsten, 2013), a greater probability of being employed (Bonnet et al., 2018), and higher self-assessed economic well-being (Augustijn, 2023). Furthermore, research demonstrated that JPC was positively linked to mothers' chances of repartnering (Schnor et al., 2017) as well as their participation in personal leisure activities outside the home-even though post-separation care arrangements were not related to the social life of fathers .
However, scholars have also argued that a negative relationship exists between JPC and the well-being of resident parents. JPC puts high demands on all family members; thus, practicing this type of care arrangement is likely to require more coordination and communication from the parents than SPC (van der Heijden et al., 2016). Because separated parents usually have a strained relationship, higher levels of post-separation contact may increase the frequency and severity of interparental conflict over time. Another argument is that organizing everyday life and coordinating their children's moves between parental households in a JPC family is a complex task requiring extensive planning from both parents (Smyth et al., 2003;Spruijt & Duindam, 2009). These additional efforts may increase parents' perception of stress and time pressure (Smyth et al., 2003;Spruijt & Duindam, 2009;van der Heijden et al., 2016) and thus negatively affect their overall well-being. Finally, sharing physical custody more equally with the other parent may be seen as a loss by the parent who was the child's main caregiver prior to family dissolution. In such cases, having their children live with the other parent for extended periods of time may not have a liberating effect (Cottier et al., 2017;Fritzell et al., 2020). A Swedish study found, for example, that JPC was not related to lower levels of worry and anxiety in mothers. Indeed, mothers who were living in a JPC arrangement were at a higher risk of experiencing mental health problems than their counterparts who were living in a SPC arrangement (Fritzell et al., 2020).

Joint Physical Custody and Resident Parents' Life Satisfaction
One dimension of subjective well-being for which empirical evidence regarding parents is available is life satisfaction. Unfortunately, knowledge on this topic has been generated by only a handful of studies. This lack of research is troubling given that life satisfaction is a particularly important indicator of subjective well-being, and "although happiness and life satisfaction are not synonymous, understanding factors relating to life satisfaction is crucial to understanding what makes individuals happy" (Erdogan et al., 2012(Erdogan et al., , p. 1039. In addition, life satisfaction is linked to numerous other dimensions of well-being, including sleep complaints (e.g., Brand et al., 2010) and mortality (e.g., St. John et al., 2015), with higher levels of life satisfaction being related to better outcomes.
Previous research from Sweden showed that parents with JPC had higher life satisfaction than those with SPC but lower life satisfaction than parents in nuclear families (Bergström et al., 2014). In contrast, a study from Germany found that post-separation care arrangements were unrelated to parents' satisfaction with either their family life or their financial situation after controlling for sociodemographic variables (Köppen et al., 2020). Similarly, longitudinal analyses from Germany revealed no significant associations between post-separation care arrangements and the life satisfaction of parents (Augustijn, 2022b) and fathers (Augustijn, 2022a), respectively.
Research on the mechanisms that may explain a possible link between post-separation care arrangements and parental life satisfaction is almost entirely lacking: Only one study has been carried out in this area, by Sodermans et al. (2015), which found that care arrangements were not directly related to parents' subjective well-being, measured by an index of life satisfaction, depressive feelings, and self-esteem. Instead, care arrangements indirectly affected the subjective well-being of parents in a gender-specific way. Mothers in JPC families had less open communication with their children than mothers with SPC, and less open communication was related to lower levels of well-being. By contrast, fathers with JPC experienced lower levels of negative father-child communication than their counterparts with SPC, and these levels of communication were positively related to their subjective well-being. Non-resident fathers in mother SPC families had even less negative father-child communication than those with JPC. In sum, the findings suggested that more time spent with their children gave fathers more opportunities to engage in negative parent-child communication, a pattern that was not found for mothers. To explain their findings, the authors argued that the gender-specific relationship between JPC, parent-child communication, and parents' subjective well-being may result from the different family roles played by mothers and fathers. The hypothesis was that fathers' "more controlling functions, like setting boundaries […] could explain their higher communication difficulties with their resident children" (Sodermans et al., 2015, p. 271). Accordingly, this study indicated that it is more difficult for fathers to fulfill their role as a resident parent after family dissolution than it is for mothers.
While there is at least some evidence that the quality of the parent-child relationship can explain the positive association between JPC and parents' life satisfaction, similar research on the quality of the interparental relationship is still almost completely lacking. In fact, only one study from Sweden has commented on the role of interparental conflict when investigating parental life satisfaction in different post-separation family types. Van der Heijden et al. (2015) found that mothers and fathers with JPC reported higher life satisfaction than their respective counterparts in families in which the mother had SPC. Whereas the authors did not test explicitly for the role that interparental conflict played in this association, their findings suggested that conflict in combination with the parent-child relationship and the parents' engagement in leisure activities accounted for most of the differences in life satisfaction among parents.
To explain a relationship between post-separation care arrangements, the quality of the interparental relationship, and resident parents' life satisfaction, two associations need to be considered: (1) Post-separation care arrangements and the quality of the interparental relationship Bauserman (2012) has suggested that JPC-or the prospect of having JPC after family dissolution-may improve the interparental relationship by lessening or eliminating the parents' incentives to fight over physical custody: "[Sole custody] could promote adversarial relations in divorce by creating a perception that one parent must 'win' and the other 'lose' custody. If [joint custody] helps alleviate this view of custody, then it might be reflected in lower interparental conflict" (Bauserman, 2012, p. 466). Another argument for a better interparental relationship in JPC families refers to the need to understand families as systems in which the individual subsystems are not independent of, but mutually influence, each other (Cox & Paley, 1997, 2003. Assuming that the interparental relationship is not independent of but, to some degree, influenced by parent-child relationships, JPC may have an indirect positive effect on the relationship between the separated parents because this arrangement-through higher levels of contact-may benefit the quality of the non-resident parent-child relationship (Bastaits & Pasteels, 2019). However, it can also be argued that practicing JPC increases the likelihood of interparental conflict because higher levels of non-resident parent-child contact may lead to more contact between the parents, and "contact provides opportunities for conflict to occur" (Amato & Rezac, 1994, p. 193).
(2) The quality of the interparental relationship and parents' life satisfaction. The divorcestress-adjustment perspective proposed by Amato (2000) conceptualizes family dissolution as a process that requires adjustment from both children and parents. According to this model, the relationship between family dissolution and adjustment is mediated by several stressful events that can have various negative outcomes with respect to well-being. Because the family system undergoes fundamental reorganization after a parental breakup, family relationships are usually a significant source of strain (Tschann et al., 1989). Unlike former couples without children, parents usually have to maintain at least some level of contact after separation (Leopold & Kalmijn, 2016). However, having an interparental relationship that is characterized by frequent conflict and coparenting problems may be a significant (because constant) stressor for these parents.
Empirical studies have corroborated this assumption to some extent by showing that the quality of co-parenting and the frequency of interparental conflict are indeed related to adult well-being (see, e.g., Lamela et al., 2016;Masheter, 1991;Maslauskaitė & Steinbach, 2020;Symoens et al., 2014). Evidence on this topic is sparse, however, given that the vast majority of studies on co-parenting and interparental conflict have considered the well-being of children rather than that of adults.
Discussions of arguments for a causal relationship between post-separation care arrangements, the quality of the interparental relationship, and parents' life satisfaction must consider the relevance of selection processes. Parents with JPC may form a positively selected group of parents or, in other words, they may differ from parents who choose SPC with respect to several characteristics that positively affect their wellbeing. Research has shown, for instance, that parents with JPC have, on average, higher educational levels (Juby et al., 2005;Sodermans et al., 2013) and higher incomes (Cancian et al., 2014;Meyer et al., 2017) than parents with SPC. Selection processes may also be relevant with respect to the quality of co-parenting and the frequency of interparental conflict, since parents with a better interparental relationship may be more willing to share physical custody of their children equally after family dissolution than parents with a more conflicted relationship (Poortman & van Gaalen, 2017). The issue of self-selection may be particularly relevant in countries such as Germany, where the prevalence of JPC is low and there is a lack of institutional support for this care arrangement, including legal regulations that do not encourage parents to practice it (see also Sodermans et al., 2013). Based on the available research and arguments discussed in this study, the statistical analyses will test two hypotheses. The first is that parents who practice JPC have higher life satisfaction than parents who practice SPC (H 1 ), while the second states that the association between JPC and parents' life satisfaction can be fully explained by the quality of co-parenting and the frequency of interparental conflict (H 2 ).

Data
The statistical analysis draws on data from the Family Models in Germany (FAMOD) survey , a convenience sample of 1,554 nuclear and post-separation families conducted between 2019 and 2020. The survey's primary objective was to explore the well-being of parents and children living in post-separation families across Germany, although the study's primary focus was on families with a JPC arrangement. The FAMOD survey was designed as a multi-actor study and collected information from different groups of participants. One of these groups consisted of parental respondents with at least one biological child under the age of 15. These respondents were also referred to as anchor respondents, and over the course of a computer-assisted personal interview (CAPI), data on a broad range of topics, including the respondents' well-being, their separation from the other biological parent of their child, and their sociodemographic makeup, were collected. During the anchor interview, one of the respondents' children was selected as a target child. Detailed information was collected about this particular child, for example on his or her post-separation care arrangement. For a post-separation family to be included in the FAMOD survey, the target child had to have contact with both biological parents (for more detailed descriptions, see Kantar Public, 2020; Steinbach et al., 2020).

Sample
Given that the focus of this study was on parents in post-separation families, all nuclear families (n = 321) were deleted from the sample. In addition, all parents who reported not having contact with the other parent of the target child were excluded (n = 48) as information on the quality of co-parenting and the frequency of interparental conflict could not be obtained from this group. Moreover, all cases with missing values on the independent variable (i.e., the post-separation care arrangement; n = 55) and the dependent variable (i.e., the parents' life satisfaction; n = 2) were deleted. Finally, because the low number of non-resident parents did not allow for a comparison with their resident counterparts, all non-resident parents were excluded from the analysis (n = 24). As a result, the sample consisted only of parents who spent at least 50% of the time with their children after family dissolution. All missing values on the mediator variables (i.e., the quality of co-parenting and the frequency of interparental conflict; n = 46) and the covariates (n = 49) were imputed by means of median imputation (median values being calculated separately for post-separation care arrangements), resulting in an analytical sample of 1,104 resident parents practicing either SPC or JPC.

Dependent Variable
The dependent variable in this study was the parent's life satisfaction. As the cognitive and evaluative component of subjective well-being, life satisfaction can be defined as "a global judgment that people make when they consider their life as a whole" (Diener, 1994, p. 107). This judgment differs from the affective component of subjective well-being, which is measured by the experience of positive and negative emotions (Diener, 1994). Conceptualized as the stable component of subjective well-being, life satisfaction remains generally uninfluenced by short-term emotions (Levin et al., 2012). In the FAMOD study, parental life satisfaction was measured with a commonly used global 11-point rating scale for the following question: "All in all, how satisfied are you with your life at the moment?" The response categories for this item ranged from very dissatisfied (1) to very satisfied (11), with higher values on this item indicating higher levels of parental life satisfaction.

Independent Variable
The independent variable was the post-separation care arrangement practiced by the parent. This variable was assessed with a so-called residential calendar (see Sodermans et al., 2014) that allows different types of post-separation care arrangements to be clearly distinguished. First, each anchor respondent received a calendar in which he or she indicated how many days and nights the target child spent with either the mother or the father during two weeks of a typical month. If these two weeks were unrepresentative of the whole month, the respondent received a second calendar displaying the last two weeks of the month. If the target child was living more than 70% of the time (i.e., days and nights) with the anchor respondent, the respondent was practicing SPC (0). If the target child was spending between 50 and 70% of the time with the anchor respondent, he or she was practicing JPC (1).

Mediator Variables
The two mediator variables were the quality of co-parenting and the frequency of interparental conflict. Co-parenting is "a conceptual term that refers to the ways that parents […] relate to each other in the role of parents […] and consists of the support and coordination (or lack of it) that parental figures exhibit in childrearing" (Feinberg, 2003, p. 96). To measure the quality of co-parenting between the separated parents, the respondents were given the following text: "Please tell me how often the following statements are true for you and the biological father/mother of [target child]. Please think about the current situation regarding [target child]." Based on the response categories never (1) to very often (5), the respondents assessed six items intended to capture the degree of co-parenting support (see also Karberg & Cabrera, 2020;Waller, 2012): "When the biological father/mother is with your child, he/she acts like the father/mother you want for your child" (Item 1); "The biological father/mother can be trusted to take good care of your child" (Item 2); "The biological father/mother respects the schedules and rules you make for your child" (Item 3); "The biological father/mother supports you in the way you want to raise the child" (Item 4); "You and the biological father/mother can talk about problems that come up with raising your child" (Item 5); and "You can count on the biological father/mother for help when you need someone to look after your child for a few hours" (Item 6; α for a mean scale consisting of all items: 0.92).
To determine the frequency of interparental conflict, the following question was asked: "How often do the following things occur between you and the biological father/mother of [target child] today?" Again, the respondents answered five items with the help of the response categories never (1) to very often (5). The five items were as follows (see also Poortman, 2018;van der Heijden et al., 2016): "There are tensions or differences of opinion between you and the other biological parent" (Item 1); "There are heated discussions between you and the other biological parent" (Item 2); "One of you strongly blames the other" (Item 3); "You don't want to talk with each other for a while" (Item 4); and "Arguments get out of hand" (Item 5; α for a mean scale consisting of all items: 0.88).

Covariates
The parent's sex was either female (0) or male (1). The parent's age ranged from 20 to 58 years. The parent's educational level was assessed on the basis of the respondents' general school-leaving certificate, with the sample being divided into three groups: low educational level (0, at maximum the lowest formal qualification of Germany's tripartite secondary school system); medium educational level (1, intermediary secondary qualification); and high educational level (2, at minimum a certificate fulfilling the entrance requirements for a university of applied sciences). To determine the parent's partnership status, the sample was split in two groups: no partner (0) and partner (1). The parent's number of children was assessed with the question: "How many children do you have?" This question aimed to include all children who were currently living or had ever been living in the respondent's household, including biological children and adopted children. The number ranged from one to six children. The age of the parent's youngest child ranged from zero to 14 years. The time since the separation from the child's other parent was measured by subtracting the year in which the relationship between the former partners ended from the year of data collection, with the amount of time that had elapsed ranging from zero to 15 years.

Analytical Strategy
This study used structural equation modelling (SEM) to examine the association between post-separation care arrangements and parental life satisfaction and to investigate whether the quality of co-parenting and the frequency of interparental conflict mediate this association. Statistical analyses were carried out with STATA 17, using a maximum likelihood (ML) estimation. SEM was chosen to test this study's hypotheses because this statistical method allows investigation of the relationships between a number of different variables in a single model, including latent/unobserved variables and indicator/observed variables, which can be either continuous or categorical. Moreover, unlike OLS regression models, structural equation models enable researchers to differentiate between direct and indirect effects and, thus, to conduct mediation analysis. Another advantage of SEM is that several fit indices can be used to judge the overall fit of the estimated models (Page, 2018).
To test the robustness of the findings, sensitivity analyses were carried out for a subsample of parents with only one type of post-separation care arrangement. Because only a very small number of anchor respondents reported practicing both SPC and JPC at the time of data collection (n = 12), the subsample was just marginally smaller than the full sample and consisted of 1,092 families. Unsurprisingly, the results of the structural equation models for this subsample did not differ substantially from the results obtained for the full sample. Additional robustness checks also showed that the results of the statistical analyses did not depend on whether missing values were imputed by means of median imputation or multiple imputation (n = 1,104) or were listwise deleted (n = 1009; results are not shown but available on request).

Results
The descriptive sample statistics for all variables-presented separately for post-separation families, SPC families and JPC families-are displayed in Table 1. Of the 1,104 families included in the analytical sample, 661 practiced SPC (59.9%) and 443 practiced JPC (40.1%). The descriptive findings also show that parents with JPC had slightly higher life satisfaction scores (M = 9.2) than parents with SPC (M = 8.8). With a 0.4-point difference on an 11-point rating scale, the difference between the two groups was relatively small, however, and a mean of 8.9 for all post-separation families suggests that the parents generally had a positive assessment of their life satisfaction. Parents with JPC reported higher levels of co-parenting and lower levels of interparental conflict on each item than parents with SPC, and the differences between the two groups of parents were more pronounced with respect to their assessment of the co-parenting quality. Another noticeable finding is that more parents with JPC had a high educational level (difference of 9.4 percentage points) and fewer had a low educational level (difference of 7.9 percentage points) than their counterparts with SPC. Finally, it appears that the separation from their child's other parent occurred longer ago for parents with SPC (M = 4.1 years) than for parents with JPC (M = 3.6 years). Figure 1 presents the results of the multivariate structural equation models. Model 1 shows the relationship between post-separation care arrangements and parents' life satisfaction prior to the inclusion of the mediator variables; Model 2 shows the full model in which the quality of co-parenting and the frequency of interparental conflict were considered. Both models were adjusted for the parent's sex, age, educational level, partnership status, and number of children, as well as for the age of the parent's youngest child and the amount of time that had elapsed since separation from the target child's other biological parent. The goodness-of-fit measures for both structural equation models suggest that the fit is acceptable to good (see, for example, Hu & Bentler, 1999;Schermelleh-Engel et al., 2003).
Model 1 revealed a significant relationship between post-separation care arrangements and parents' life satisfaction (β = 0.09, p < 0.01); that is, parents with JPC reported higher average levels of life satisfaction than their counterparts with SPC. However, the standardized regression coefficient suggested that this relationship was comparatively weak. Nevertheless, this finding confirmed the first hypothesis of this study by demonstrating that parents who practiced JPC had higher life satisfaction than those who practiced SPC (H 1 ). In Model 2, we can see that the six items measuring the quality of co-parenting and five items measuring the frequency of conflict between the separated parents loaded on respective latent measures. The factor loadings for co-parenting quality ranged from 0.75 to 0.89 (all items: p < 0.001), and the factor loadings for frequency of interparental . Note Family Models in Germany (FAMOD); ***p < 0.001; **p < 0.01; *p < 0.05. Controls: parent's sex, age, educational level, partnership status, and number of children, age of the parent's youngest child, and time since separation from the target child's other parent conflict ranged from 0.65 to 0.87 (all items: p < 0.001). In the full structural equation model, the relationship between post-separation care arrangements and parents' life satisfaction was no longer significant (β = − 0.03). Instead, the findings indicate that practicing JPC was positively associated with the quality of co-parenting (β = 0.38, p < 0.001) and negatively with the frequency of interparental conflict (β = − 0.13, p < 0.001). Increasing levels of co-parenting quality were, in turn, related to higher levels of parental life satisfaction (β = 0.26, p < 0.001), whereas increasing levels of interparental conflict were related to lower levels of parental life satisfaction (β = − 0.17, p < 0.001). In sum, these findings show that the quality of co-parenting and the frequency of interparental conflict fully mediated the association between post-separation care arrangements and parental life satisfaction. Those with JPC had a better co-parenting relationship and experienced fewer interparental conflicts, two factors which were associated with higher levels of life satisfaction. Consequently, the second hypothesis was also confirmed: The association between JPC and parents' life satisfaction can be fully explained by the quality of co-parenting and the frequency of interparental conflict (H 2 ).
With respect to the covariates, the results of the full structural equation model showed that only one variable was related to life satisfaction: partnership status. Respondents with a partner had, on average, higher levels of life satisfaction than respondents who were not in a relationship (β = 0.33, p < 0.001). By contrast, no significant relationships were found between the parents' life satisfaction and their sex, age, educational level, number of children, age of the youngest child, or amount of time that had elapsed since the separation from the other biological parent (results are not shown, but available on request).

Discussion
Because growing numbers of children in post-separation families spend considerable amounts of time with both their mother and father after family dissolution, the link between post-separation care arrangements and children's well-being has received some attention from researchers. However, one question that has been neglected is whether postseparation care arrangements affect the well-being of parents and, if so, how. To help close this research gap, the current study investigated the relationship between post-separation care arrangements-JPC and SPC-and the life satisfaction of resident parents and tested the possible mediating roles of the co-parenting quality and the frequency of interparental conflict, using data from Germany, a country in which JPC is not as widespread as in other Western countries (Steinbach et al., 2021). The goal of the analysis was to answer two research questions: Is practicing JPC associated with parents' life satisfaction? Can the quality of co-parenting and the frequency of interparental conflict explain this association?
The findings of the structural equation models showed that parents with JPC experienced higher average levels of life satisfaction than parents with SPC. The results also indicated that the relationship between JPC and life satisfaction could not be explained by sociodemographic characteristics, which in this study included the parents' sex, age, educational level, partnership status, and number of children, as well as the age of the parent's youngest child and the amount of time that had elapsed since separation from the target child's other parent. After the quality of co-parenting and frequency of interparental conflict were included in the structural equation model, however, the direct relationship between post-separation care arrangements and life satisfaction became insignificant. Instead, the full model showed that post-separation care arrangements were only indirectly related to parents' well-being via the quality of co-parenting and the frequency of interparental conflict. Parents with JPC reported higher levels of co-parenting support and lower levels of interparental conflict. The two indicators of the interparental relationship quality were, in turn, significantly related to parental life satisfaction: The higher the quality of coparenting, the higher the parents' life satisfaction, and the higher the frequency of interparental conflict, the lower the parents' life satisfaction. Consequently, the quality of co-parenting and the frequency of interparental conflict fully mediated the relationship between post-separation care arrangements and parental life satisfaction, a finding that corroborates the assumption that the well-being of parents in post-separation families is related to certain key aspects of the interparental relationship.
The central findings of this study largely corroborate the findings of earlier studies, which showed that parents with JPC had higher levels of life satisfaction than parents with SPC (Bergström et al., 2014), and that interparental conflict mediated the positive association between JPC and parental life satisfaction (van der Heijden et al., 2015). Nonetheless, interparental conflict seemed to play a more important role in explaining the link between JPC and parental life satisfaction in the present study. However, when comparing findings from Germany and Sweden, it needs to be kept in mind that societal contexts (in general) and the prevalence of JPC (in particular) differ across the two countries. Because these different contexts may affect the relationship between post-separation care arrangements and parents' life satisfaction, similar findings may conceal important differences (e.g., differences regarding selection mechanisms). A rather surprising finding was that the present study diverges from earlier studies that examined life satisfaction among separated parents with JPC and SPC living in Germany. The results of the structural equation models, for example, contradicted those obtained by Augustijn (2022b), who found that resident parents with JPC did not differ from those with SPC in terms of life satisfaction. Moreover, in the present study, sociodemographic characteristics did not explain the association between post-separation care arrangements and parental life satisfaction as they did in the study by Köppen et al. (2020). However, it should be noted that in these last two studies, postseparation care arrangements could not be distinguished with high precision, due to the relatively crude measurements that were employed in the German Family Panel (pairfam), the survey on which both studies were based. Therefore, it cannot be ruled out that different measurements explain the somewhat contradictory findings either partially or fully.

Limitations
Although this study has several strengths, including the use of a residential calendar that allowed for a clear distinction to be made between SPC and JPC families, its findings need to be interpreted against some limitations. One limitation is that the FAMOD study was designed as a convenience sample. JPC is still a rare phenomenon in Germany, with only up to 5% of post-separation families practicing this type of care arrangement (Walper et al., 2021). Therefore, drawing a random sample of post-separation families was not feasible and would not have ensured that sufficient numbers of families with JPC were included. However, although the FAMOD study is not representative of post-separation families in Germany, research has shown that the anchor respondents in this survey resembled the respondents from other surveys whose key sociodemographic characteristics were representative of the German population of separated or divorced parents . A second limitation is that the post-separation families included in the FAMOD study were families in which the target child had contact with both biological parents. Thus, these families form a somewhat positively selected group, that is, families in which the non-resident parent maintained at least some involvement in his or her child's life.
A third limitation is that non-resident parents could not be considered in the statistical analysis due to their very low numbers in the FAMOD sample. This is unfortunate because it is important to consider the well-being of all family members when investigating post-separation care arrangements, and a comparison of resident and non-resident parents may yield further insights into post-separation family life. Fourth, the items that were used to measure the quality of co-parenting between the biological parents captured only one dimension of co-parenting, namely co-parenting support. Co-parenting, however, is usually conceptualized as a multidimensional construct. Teubert and Pinquart (2010), for instance, differentiated between four aspects of co-parenting: cooperation, childrearing agreement, conflict, and triangulation. Therefore, it would have been a significant advantage had this study been able to consider other dimensions of co-parenting in addition to co-parenting support. Fifth, because this study was based on cross-sectional data, the causal relationships among the independent, mediator, and dependent variables could not be determined. The use of cross-sectional data does not allow researchers to examine how changes in the type of care arrangement or quality of the interparental relationship affect the life satisfaction of parents. Moreover, as discussed earlier, arguments for a causal relationship between post-separation care arrangements and the well-being of parents always need to be interpreted against the possibility that an observed link is the outcome of selection processes among post-separation families (Emery, 2021;Smyth et al., 2016).

Concluding Remarks
Despite its limitations, the present study made an important contribution to our knowledge regarding parents' well-being in SPC and JPC families by showing that post-separation care arrangements are related to parental life satisfaction not directly but indirectly, through the quality of co-parenting and the frequency of interparental conflict. This finding, of course, raises the central questions of whether JPC has the potential to enhance the quality of co-parenting and decrease levels of interparental conflict or whether selection processes can explain the positive relationships between JPC and these two indicators of the interparental relationship quality. On the one hand, it has been argued that JPC may alleviate or even eliminate conflicts between parents, especially when it comes to the question of how to divide the physical custody of a child after family dissolution. Better parent-child relationships in a JPC family may also positively affect the quality of the interparental relationship, given that family relationships are interrelated. On the other hand, the lack of institutional support for JPC in Germany makes it likely that families who practice this care arrangement are indeed a self-selected group with several positive characteristics that contribute to the success of JPC. As a result, it cannot be ruled out that the positive association between JPC and parental well-being that was found in this study will change if the legal framework for physical custody in Germany is reformed in the future. In Belgium, for example, joint legal custody and JPC became the legal defaults in 1995 and 2006, respectively. Based on their analysis, Sodermans et al. (2013) concluded: Before 1995 joint physical custody was significantly associated with low parental conflict.
[…] However, the association between parental conflict and the custody arrangement was absent for couples that divorced after 1995. In the last divorce cohort the direction of the association reversed, but this association was not statistically significant. (Sodermans et al., 2013, p. 833).
Similar developments can be expected for Germany, in which case JPC may no longer be beneficial for many post-separation families; a possibility to which policy makers should pay close attention.
Although this study cannot comment on the question of causation vs. selectivity with certainty, the results of the statistical analysis nevertheless suggest that family relationships in post-separation families are more important factors to consider when investigating parents' subjective well-being than the type of post-separation care arrangement these families practice, and this has further implications for policy makers and practitioners. Instead of focusing exclusively on increasing the number of families who practice JPC, policies and treatments should be designed in such a way that all separated or divorced parents-regardless of care arrangements-have the opportunity to enhance their post-separation relationship. This goal may be achieved through, for example, additional offers of mediation and counseling with an even stronger focus on the relationship between the parents (for an overview of co-parenting interventions in JPC families, see Darwiche et al., 2021). Raising awareness of the personal benefits that can result from a positive relationship with the other parent may increase parents' incentive to participate in these interventions. Another advantage of such an approach is that improving the interparental relationship will likely benefit not only parents but also children, given that previous studies have shown that co-parenting and interparental conflict are-under certain circumstances-related to child well-being (Herrero et al., 2020;Karberg & Cabrera, 2020). In addition, this study confirms the need for family courts to pay special attention to the quality of family relationships when making decisions about post-separation care arrangements.
Given the limitations of most studies on JPC, future studies aimed at investigating parents' well-being in different types of post-separation families should focus particularly on the question of causality. While sharing physical custody more equally with the other parent offers some advantages for the resident parent-advantages that may contribute to a better relationship between the parents-it is quite plausible that selection processes play at least some role in shaping parents' choice of post-separation care arrangements. To determine the causal relationship between care arrangements and the quality of the interparental relationship, additional studies based on longitudinal data are needed to examine the relationship before and after separation or divorce. In addition, future studies should attach more importance to exploring factors that may mediate or moderate the relationship between post-separation care arrangements and parental well-being, including parents' and children's satisfaction with their care arrangement. Studies that investigate both parents (i.e., mothers and fathers) and children are also urgently needed to provide a more comprehensive view of well-being in post-separation families.
Funding Open Access funding enabled and organized by Projekt DEAL. This work was supported by the German Research Foundation under Project Number 394377103.

Conflict of interest
No potential conflict of interest was reported by the author.