Archives of Sexual Behavior

, Volume 22, Issue 3, pp 187–206

Homosexual orientation in twins: A report on 61 pairs and three triplet sets


  • Frederick L. Whitam
    • Department of SociologyArizona State University
  • Milton Diamond
    • Department of Anatomy and Reproductive Biology, John A. Burns School of MedicineUniversity of Hawaii
  • James Martin
    • Department of SociologyArizona State University

DOI: 10.1007/BF01541765

Cite this article as:
Whitam, F.L., Diamond, M. & Martin, J. Arch Sex Behav (1993) 22: 187. doi:10.1007/BF01541765


Twin pairs in which at least one twin is homosexual were solicited through announcements in the gay press and personal referrals from 1980 to the present. An 18-page questionnaire on the “sexuality of twins” was filled out by one or both twins. Thirty-eight pairs of monozygotic twins (34 male pairs and 4 female pairs) were found to have a concordance rate of 65.8% for homosexual orientation. Twenty-three pairs of dizygotic twins were found to have a concordance rate of 30.4% for homosexual orientation. In addition, three sets of triplets were obtained. Two sets contained a pair of monozygotic twins concordant for sexual orientation with the third triplet dizygotic and discordant for homosexual orientation. A third triplet set was monozygotic with all three concordant for homosexual orientation. These findings are interpreted as supporting the argument for a biological basis in sexual orientation.

Key words

homosexualitytwinstripletssexual orientationgenetics

Copyright information

© Plenum Publishing Corporation 1993