title: Homosexuals who are twins. A study of 46 probands.
abstract: Forty-six homosexual men and women who were twins took part in a study of their sexuality and that of their co-twin. Discordance for sexual orientation in the monozygotic pairs confirmed that genetic factors are insufficient explanation of the development of sexual orientation. There was a high level of shared knowledge of sexual orientation between members of twin pairs, and a relatively high likelihood of sexual relations occurring with same sex co-twins at some time, particularly in monozygotic pairs. The implications of these results for the study of the origins of sexual orientation and for twin research are discussed.
authors.affiliation: Royal Free Hospital School of Medicine, London.
authors.forename: M
authors.initials: M
authors.lastname: King
authors.forename: E
authors.initials: E
authors.lastname: McDonald
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006716:Homosexuality / Q000523:psychology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012725:Sexual Behavior; D012801:Sibling Relations; D012931:Social Environment; D014429:Twins, Dizygotic / Q000235:genetics* / Q000523:psychology; D014430:Twins, Monozygotic / Q000235:genetics* / Q000523:psychology