I believe yes that it is caused by various genetic "traits" that hold influence in certain family-lines, not that it is genetic in the sense of, "I have brown eyes or blue eyes so my son or daughter will have them." I'm a male Homosexual, and I do have oe older brother (Fraternal-Birth Order Affect) and my Mother and her Maternal line all medically have a "Hyper-Fecund" reproductive success, something that was said to be a great possible cause by Prof. A. Camperio-Ciani. I also have on the Maternal side a 2ND cousin Lesbian and two 4TH cousin Lesbians who are sisters.

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