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

Archives of Sexual Behavior volume 22, pages 187–206 (1993)Cite this article

Abstract

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.

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Authors and Affiliations

  1. Department of Sociology, Arizona State University, 85287-2101, Tempe, Arizona, USA

    Frederick L. Whitam Ph.D. & James Martin B.A.

  2. Department of Anatomy and Reproductive Biology, John A. Burns School of Medicine, University of Hawaii, 1951 East-West Road, 96822, Honolulu, Hawaii, USA

    Milton Diamond Ph.D.

Authors
  1. Frederick L. Whitam Ph.D.
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  2. Milton Diamond Ph.D.
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  3. James Martin B.A.
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Whitam, F.L., Diamond, M. & Martin, J. Homosexual orientation in twins: A report on 61 pairs and three triplet sets. Arch Sex Behav 22, 187–206 (1993). https://doi.org/10.1007/BF01541765

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Key words

  • homosexuality
  • twins
  • triplets
  • sexual orientation
  • genetics