It isn't a choice. You are born that way, or something makes you go that way. Honestly, I think that something could in effect cause someone to turn a straight man or woman homosexual, or a gay man or woman straight. Maybe when they're developing, or due to some kind of trauma, but I'm not willing to put it past that. Unless there is actually a gay gene, then I think this is true.
You might not be born gay. That's what I believe. But, it isn't a choice. If it was people like Seth Walsh wouldn't have killed themselves over being bullied and teased. They got some of the worst of it, and after do you think that they'd still choose to be gay? Doubt it. There was this one gay guy who going through school, people would beat the crap out of him, push him in urinals, and molest him because he was gay. Do you still think that he'd choose to live a life like that? I don't.
I'm not saying you're born that way, I'm not saying I know what causes it. But what I can say for 100% ascertainment, being gay is NOT a choice. Have a nice day.
As for what causes it, that's one of those questions that I don't much care about the answer to. We're here, we're queer, get used to it. I hope people don't find out the answer, because this might be the end of the Gay community as we know it if they can stop it. Make it so the child comes out straight. Which I believe would be inhuman and shouldn't be done.