Serious Question: Please Answer Honestly (no straight people answer)?

I was having a debate with my coworker whose brother is gay, from what ive been told, gay people are born that way, but she thinks her brother is like this because their mother was a controlling narcissistic *****. what the hell does that have to do with it? i want to prove, parents cant MAKE their child gay, you cant MAKE someone gay, too many people have told me they are born that way, and the last thing it would be based on is the relationship with their parents since most people come out as teenagers and at that age you dont care what youre parents say anyway. and all the gay people i know have awesome parents! whats not to like growing up in a upper-middle cl family, the best catholic school and a nice suburb, cmon now?? so my question did your relationship with your parents or something else in your environment effect your uality or is it like the scientist say: pure genetics???