My experience is similar to John's.
I knew when I was 10 that I was very attracted to males, my uncles, the other boys in the neighborhood, football players on TV. My attraction was always to the big husky masculine guys and this hasn't changed for my entire life.
I don't believe there is one gene that just clicks on and makes you homosexual. I think it is probably a combination of genes and other circumstances that determines exactly where on the range of homo/heterosexuality one falls.
As I've said before, being active on the internet I have ran into 100s of married men who enjoy male/male sex on the side. You just don't see this covered in the media so people say, oh that's just gays trying to up their numbers. I can only speak from personal experience when I say that it appears to me there are lots of bisexuals out there. Bisexuals clearly choose who they want to have sex with since they are stimulated by both and many choose to have sex with both. I don't know of any male/male couples where one of them goes and sneaks some girl fun on the side, so it appears that heterosexual sex doesn't fill as many needs for bisexuals as homosexual sex does.
I don't know any homosexual who believes they chose their sexuality. Clearly, we choose whether or not to act on it and most of us do. Show me a celibate homosexual and I'll show you a miserable homosexual.
You could force me to marry a woman in order to fit into some societally accepted regimen of behavior, but I can assure you that woman would not be a happy camper.
Again, in my experience, there is also a very large contingent who do it completely secretly, either through internet rendezvous, bookstore stall, parks and rest areas or just waiting til they are on a business trip to get some away from home.
Most of my homosexual friends are closer to their mothers, but I think that's because they are homosexual. I think most people just get the cause and effect out of order. We aren't homosexuals because we were close to our mothers, we were close to our mothers because we are homosexuals.
Sex is a spectrum. You can't bottle it up into a behavioral code. We are animals after all.
hugs
Joel