FAMILIALITY OF FEMALE AND MALE HOMOSEXUALITY

We examined data from a large cohort of homosexual and heterosexual fe males and males concerning their siblings' sexual orientations. As in previous studies, both male and female homosexuality were familial. Ho mosexual females had an excess of homosexual brothers compared to hete roxual subjects, thus providing evidence that similar familial factors influence both male and female homosexuality. Furthermore, despite th e large sample size, homosexual females and males did not differ signi ficantly from each other in their proportions of either homosexual sis ters or homosexual brothers. Thus, results were most consistent with t he possibility that similar familial factors influence male and female sexual orientation. However, because results conflicted with those of some other studies, and because siblings' sexual orientations were ob tained in a manner likely to yield more errors than in these other, sm aller studies, further work is needed using large samples and more car eful methods before the degree of cofamiliality of male and female hom osexuality can be resolved definitively. We also examined whether some parental influences comprised shared environmental effects on sexual orientation. Scales attempting to measure such influences failed to di stinguish subjects with homosexual siblings from subjects with only he terosexual siblings and, thus, did not appear to measure shared enviro nmental determinants of sexual orientation.