Archives of Sexual Behavior

, Volume 22, Issue 3, pp 187–206 | Cite as

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

  • Frederick L. Whitam
  • Milton Diamond
  • James Martin


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

homosexuality twins triplets sexual orientation genetics 


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Copyright information

© Plenum Publishing Corporation 1993

Authors and Affiliations

  • Frederick L. Whitam
    • 1
  • Milton Diamond
    • 2
  • James Martin
    • 1
  1. 1.Department of SociologyArizona State UniversityTempeUSA
  2. 2.Department of Anatomy and Reproductive Biology, John A. Burns School of MedicineUniversity of HawaiiHonoluluUSA

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