I have an acquaintance whose mother is a lesbian and he says she had a partner until quite recently, and he seems a bit, ah, homosexual and estranged.

However, I think that having such parents is not enough to turn someone gay, perhaps give them certain opinions and tastes and manners and such, but not actually to make them want sodomy. I believe it is the environment around the child until the end of puberty which affects whether or not the child will end up gay.