Well, that depends on you. Some people figure it out when they're in their teens, when they're young adults, and some even when they were little. Sometimes it's a process of understanding and figuring yourself out.
Sexuality is actually pretty complex for some people. آپ could be a grey-a asexual who's attracted to woman, آپ could be a gay man who's attracted to transmen, آپ can be a lesbian and only be attracted to women, it's all narrowed down to personal preference. All I can say is, you'll know one day.
I'm still figuring things out myself. I consider myself a grey-a pansexual, (grey-a: not as sexually influenced as others, but not completely repulsed سے طرف کی sex. pansexual: attracted to personality مزید than gender)- however, I'm discovering that I might be مزید into girls. A lot more. But I have identity issues, and my tastes and گیا پڑھا مرتبہ change rapidly at times, so I'm afraid to call myself anything else.
i think sexuality just grows on us as we grow up, maybe we are always changing, maybe someone may have a gay phase one دن and then be attracted to a woman and marry her, یا something like that, i think it may be biological for some people but im not counting on it. I don't know how آپ know if your gay, lesbian یا bi, because i don't know what i am, i think most people have a little bit of everything in them, and then when they get older, some people might have a little مزید of something than something else like, a little مزید gay than straight یا straight than gay یا bi یا something, and yeah i guess some people might have مزید girlish genes یا manly genes, but i don't think that has much to do with it, i think love has مزید to do with it but im not sure