Age you know you're gay?

[Estu]

This is a question for any gay people out there, or people who have close gay friends. At what age does a person realize they are attracted to members of the opposite sex rather than members of the same sex? I know that some version of romantic attraction is common at young ages, like, say, a seven year old boy "liking" a seven year old girl. But maybe this is just because he sees boy-girl pairings and copies them - could this boy then, five years later, hit puberty and realize he actually likes boys and not girls? Is this the situation most of the time, or do even seven year old gay boys and girls already start developing crushes on the same sex?