Archives of Sexual Behavior

, Volume 29, Issue 4, pp 349–356 | Cite as

Birth Order in a Contemporary Sample of Gay Men

  • David W. Purcell
  • Ray Blanchard
  • Kenneth J. Zucker


The birth order of a contemporary North American sample of 97 gay men was quantified using Slater's Index. For the 84 probands with at least one sibling, the results showed a late mean birth order compared with the expected value of .50. Additional birth order indices derived from Slater's Index suggested that the mean later birth order was accounted for more strongly by the proband's number of older brothers than by his number of older sisters. The present findings constitute a replication of a series of recent studies and add to the growing body of evidence that birth order is a reliable correlate of sexual orientation in males.

birth order sex ratio sexual orientation homosexuality males 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bailey, J. M., Pillard, R. C., Dawood, K., Miller, M. B., Farrer, L. A., Trivedi, S., and Murphy, R. L. (1999). A family history study of male sexual orientation using three independent samples. Behav. Genet. 29: 79–86.Google Scholar
  2. Bailey, J. M., and Zucker, K. J. (1995). Childhood sex-typed behavior and sexual orientation: A conceptual analysis and quantitative review. Dev. Psychol. 31: 43–55.Google Scholar
  3. Bell, A. P., Weinberg, M. S., and Hammersmith, S. K. (1981). Sexual Preference: Its Development in Men and WomenIndiana University Press, Bloomington.Google Scholar
  4. Berglin, C.-G. (1982). Birth order as a quantitative expression of date of birth. J. Epidemiol. Comm. Health 36: 298–302.Google Scholar
  5. Berglin, C.-G. (1985). Male antigenicity and parity. Behav. Brain Sci. 8: 442–443.Google Scholar
  6. Birtchnell, J. (1971). Birth rank and mental illness. Nature 234: 485–487.Google Scholar
  7. Blanchard, R. (1997). Birth order and sibling sex ratio in homosexual versus heterosexual males and females. Ann. Rev Sex Res. 8: 27–67.Google Scholar
  8. Blanchard, R., and Bogaert, A. F. (1996a). Homosexuality in men and number of older brothers. Am. J. Psychiatry 153: 27–31.Google Scholar
  9. Blanchard, R., and Bogaert, A. F. (1996b). Biodemographic comparisons of homosexual and heterosexual men in the Kinsey interview data. Arch. Sex. Behav. 25: 551–579.Google Scholar
  10. Blanchard, R., and Klassen, P. (1997). H-Y antigen and homosexuality in men. J. Theor. Biol. 185: 373–378.Google Scholar
  11. Blanchard, R., and Sheridan, P. M. (1992). Sibship size, sibling sex ratio, birth order, and parental age in homosexual and nonhomosexual gender dysphorics. J. Nerv. Ment. Dis. 180: 40–47.Google Scholar
  12. Blanchard, R., and Zucker, K. J. (1994). Reanalysis of Bell,Weinberg, and Hammersmith's data on birth order, sibling sex ratio, and parental age in homosexual men. Am. J. Psychiatry 151: 1375–1376.Google Scholar
  13. Blanchard, R., Zucker, K. J., Bradley, S. J., and Hume, C. S. (1995). Birth order and sibling sex ratio in homosexual male adolescents and probably prehomosexual feminine boys. Dev. Psychol. 31: 22–30.Google Scholar
  14. Blanchard, R., Zucker, K. J., Cohen-Kettenis, P. T., Gooren, L. J. G., and Bailey, J. M. (1996). Birth order and sibling sex ratio in two samples of Dutch gender-dysphoric homosexual males. Arch. Sex. Behav. 25: 495–514.Google Scholar
  15. Blanchard, R., Zucker, K. J., Siegelman, M., Dickey, R., and Klassen, P. (1998). The relation of birth order to sexual orientation in men and women. J. Biosoc. Sci. 30: 511–519.Google Scholar
  16. Bogaert, A. F. (1998). Birth order and sibling sex ratio in homosexual and heterosexual non-white men. Arch. Sex. Behav. 27: 467–473.Google Scholar
  17. Byne, W., and Parsons, B. (1993). Human sexual orientation: The biologic theories reappraised. Arch.Gen. Psychiatry 50: 228–239.Google Scholar
  18. Chahnazarian, A. (1988). Determinants of the sex ratio at birth: Review of recent literature. Soc. Biol. 35: 214–235.Google Scholar
  19. Cobb, J. A. (1914). The alleged inferiority of the first-born. Eug. Rev. 5: 357–359.Google Scholar
  20. Fedoroff, J. P., Jacques, T., Kazazic, S., and Peever, C. (1999). An Internet survey of sadomasochism: birth order and gender effects. Poster presented at the meeting of the International Academy of Sex Research, Stony Brook, NY.Google Scholar
  21. Gebhard, P. H., Gagnon, J. H., Pomeroy, W. B., and Christenson, C. V. (1965). Sex Offenders: An Analysis of TypesHarper & Row, New York.Google Scholar
  22. Green, R. (1987). The “Sissy Boy Syndrome” and the Development of HomosexualityYale University Press, New Haven, CT.Google Scholar
  23. Green, R. (2000). Birth order and ratio of brothers to sisters in transsexuals. Psychol. Med. 30 (in press).Google Scholar
  24. Hare, E. H., and Moran, P. A. P. (1979). Parental age and birth order in homosexual patients: A replication of Slater's study. Br. J. Psychiatry 134: 178–182.Google Scholar
  25. Hare, E. H., and Price, J. S. (1969). Birth order and family size: Bias caused by changes in birth rate. Br. J. Psychiatry 115: 647–657.Google Scholar
  26. Hare, E. H., and Price, J. S. (1974). Birth order and birth rate bias: Findings in a representative sample of the adult population of Great Britain. J. Biosoc. Sci. 6: 139–150.Google Scholar
  27. Jagers, P. (1982). How probable is it to be first born? and other branching-process applications to kinship problems. Mathemat. Biosci. 59: 1–15.Google Scholar
  28. James, W. H. (1987). The human sex ratio. Part 1: A review of the literature. Hum. Biol. 59: 721–752.Google Scholar
  29. Jones, M. B., and Blanchard, R. (1998). Birth order and male homosexuality: Extension of Slater's Index. Hum. Biol. 70: 775–787.Google Scholar
  30. Kinsey, A. C., Pomeroy, W. B., and Martin, C. E. (1948). Sexual Behavior in the Human MaleW.B. Saunders, Philadelphia.Google Scholar
  31. Moore, D. H., and Gledhill, B. L. (1988). How large should my study be so that I can detect an altered sex ratio? Fertil. Steril. 50: 21–25.Google Scholar
  32. Price, J. S., and Hare, E. H. (1969). Birth order studies: Some sources of bias. Br. J. Psychiatry 115: 633–646.Google Scholar
  33. Purcell, D.W. (1995). The effects of parent–child relationships on the relation between gender nonconforming behavior in childhood and psychological adjustment in adulthood. Unpublished doctoral dissertation, Emory University, Atlanta, GA.Google Scholar
  34. Slater, E. (1958). The sibs and children of homosexuals. In Smith, D. R., and Davidson, W. M. (eds.), Symposium on Nuclear SexHeinemann Medical Books, London, pp. 79–83.Google Scholar
  35. Slater, E. (1962). Birth order and maternal age of homosexuals. Lancet i: 69–71.Google Scholar
  36. Suarez, B. K., and Przybeck, T. R. (1980). Sibling sex ratio and male homosexuality. Arch. Sex. Behav. 9: 1–12.Google Scholar
  37. Tsoi, W. F., Kok, L. P., and Long, F. Y. (1977). Male transsexualism in Singapore: A description of 56 cases. Br. J. Psychiatry 131: 405–409.Google Scholar
  38. Wellings, K., Field, J., Johnson, A., and Wadsworth, J. (1994). Sexual Behaviour in Britain: The National Survey of Sexual Attitudes and LifestylesPenguin Books, London.Google Scholar
  39. Zucker, K. J., and Blanchard, R. (1994). Re-analysis of Bieber et al.'s 1962 data on sibling sex ratio and birth order in male homosexuals. J. Nerv. Ment. Dis. 182: 528–530.Google Scholar
  40. Zucker, K. J., Green, R., Coates, S., Zuger, B., Cohen-Kettenis, P. T., Zecca, G. M., Lertora, V., Money, J., Hahn-Burke, S., Bradley, S. J., and Blanchard, R. (1997). Sibling sex ratio of boys with gender identity disorder. J. Child Psychol. Psychiatry 38: 543–551.Google Scholar

Copyright information

© Plenum Publishing Corporation 2000

Authors and Affiliations

  • David W. Purcell
    • 1
  • Ray Blanchard
    • 2
    • 3
  • Kenneth J. Zucker
    • 4
    • 5
  1. 1.Department of PsychologyEmory UniversityAtlanta
  2. 2.Clinical Sexology ProgramCentre for Addiction and Mental Health—Clarke Division;Toronto
  3. 3.Department of Psychiatry, Faculty of MedicineUniversity of TorontoCanada
  4. 4.Child and Adolescent Gender Identity Clinic, Child Psychiatry ProgramCentre for Addiction and Mental Health—Clarke Division;OntarioCanada;
  5. 5.Department of Psychiatry, Faculty of MedicineUniversity of TorontoCanada

Personalised recommendations