Think of someone you know who is gay. Does he have an older brother:

[sean]

Interesting thread~~~
I haven't read everything yet, but I'm gay and I do have an older brother. Meh? ¯\_(ツ)_/¯

That said, I specifically remember being attracted to both females and males up until somewhere around the beginning of puberty, where it all got hazy and I emerged being only attracted to guys. hmmmm