Have you all seen heard of this study on gays and lesbians called "It's in the blood" from Box Turtle Bulletin. I am so intrigued.
Using a sample of over 7,000 participants, sociologists at Minot State University in North Dakota identified a correlation between sexual orientation and both blood type and Rh factor.
Heterosexual males and females exhibited statistically identical frequencies of the A blood type, while gay men exhibited a relatively low incidence and lesbians had a relatively high incidence (p < .05). In the case of the Rh factor, unusually high proportions of homosexuals of both sexes were Rh- when compared to heterosexuals (p < .06). The findings suggest that a connection may exist between sexual orientation and genes both on chromosome 9 (where blood type is determined) and on chromosome 1 (where the Rh factor is regulated). [here's the study link]