Meta-Analyses of Fraternal and Sororal Birth Order Effects in Homosexual Pedophiles, Hebephiles, and Teleiophiles

Abstract

This study investigated the relations between numbers of older brothers, numbers of older sisters, and the odds of homosexuality in later-born males, including males who are most attracted sexually to prepubescent or early pubescent children (pedohebephiles) and males who are most attracted sexually to adults (teleiophiles). The authors meta-analyzed data from 24 samples of homosexual and heterosexual men, originally reported in 18 studies, and totaling 18,213 subjects. The results confirmed that older brothers increase the odds of same-sex preference in pedohebephiles as they do in teleiophiles. They also replicated the recent finding that older sisters have a similar but weaker statistical association with the odds of homosexuality. These findings have two theoretical implications. First, the findings for older brothers and older sisters indicate some commonality in the factors that influence sexual preference in teleiophiles and those that influence sexual preference in pedohebephiles. Second, the finding for older sisters confirms a prediction stemming from the hypothesis that male fetuses stimulate maternal antibodies that increase the odds of homosexuality in later-born males. Such immunization could result from miscarried as well as full-term fetuses, and number of older sisters should correlate with number of male fetuses miscarried before gestation of the subject.

Appendix: Description of Unpublished Data from Krupp (2014)

This dataset contains sibship information on 401 help-seeking, self-referred males who participated in a first clinical interview and assessment within the Prevention Project Dunkelfeld, a German program to prevent child sexual abuse offenses and the use of child sexual abuse images (Beier et al., 2015). The number of cases with required information for present purposes was 388. These had a mean age of 37.63 years (SD = 12.11). About half the sample, 52%, had 10 years of education or less, and 48% had 11 years or more.

Subjects reported, in clinical interviews, their erotic interests with regard to biological sex (male, female, or both) and were accordingly classified as homosexual, heterosexual, or bisexual. They also reported their erotic interests with regard to age (prepubertal, early pubertal, or physically mature persons) and could accordingly be classified as pedophilic, hebephilic, or teleiophilic. Erotic age preference was captured by three, partially overlapping variables, and there were more than three categories available for final classification. Thus, for example, a subject could be classified as a pedohebephile rather than a pedophile or hebephile if he indicated erotic interest in children who were either prepubertal or early pubertal.

In the present study, we excluded self-described bisexuals, because they did not fit into the research design and because we had no hypothesis about them, and we excluded teleiophiles, because hardly any of the teleiophiles were homosexual. We also excluded subjects who described themselves as attracted both to prepubertal children and to physically mature adults, because laboratory data suggest that individuals with strong attraction to both prepubertal children and physical mature adults are less common than the other groups of interest (see Blanchard et al., 2012, Fig. 1). However, we did include subjects who described themselves as sexually attracted to the adjacent groups, pubescents and physically mature adults. These selection criteria, the only ones we ever formulated or applied to these data, were also applied to these data, without modification, in a former study (Blanchard et al., 2020). Table 1 shows that there were 168 subjects after the foregoing exclusions.