The truth is nobody can say 100% what causes homosexuality. I happen to believe some are predisposed to it. In fact I'm certain of it. I have 3 sons, one is a gay. His mother and I "knew" this almost from the time he was an infant. His role models were me and his two older brothers. We offered sufficient male role models for him to emulate, without being stupidly macho. When the kids were little there was the "normal" boy stuff always present, baseball gloves, trucks, toy guns, fishing poles and mud puddles to jump in and forts in the woods to build. He received lots of love and attention, no major trauma or event happened to make him gay. We, his family, love him, and he loves us, THAT'S what matters.
When I was a teenager, gays often got a beating or severe ridicule for no reason. I never understood that. A friend of mine who was gay (I'm not) suffered enough that he ended up killing himself in high school. I bet he's not the only one that ever did that either.
The idea that we can or should change someone's orientation is rooted in the desire to control others. I say, let it go, and accept that there are some things that can't be changed.