Depends on what view you take. One method is the Tabula En rasa, which means people are blank slates from the get go- thier sexuality is detirmined through expiereince.
Others believe we have certian biological cues, so on and so forth. I'd imagine its somewhere inbetween.
Well, if they liked it they were bisexual. I once heard that naturally, humans were bisexual. The enviroment makes one lead towards homosexuality or heterosexuality. Of course, I dont know any more deatails, though Ive speculated a lot about it.
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