I remember reading something about a twin girl having gender issues and ended up going through stuff, then she decided to switch gender x_x I don't think it was a real story tho... even tho it's supposed to be.
I think it really boils down to personality, interests and emotion types~ a guy who is interested in sewing, dancing, and expressive things will find it easier to talk with similar people. A girl who likes to play sports, tell jokes, and be kinda wild will like being with similar people~ I'm not saying that either one can't get along with different people, it's just easier for them to have deep friendships with people like that. Of course, I'm not saying any of this is absolute~
974. The most common reasons I see people hang around with each other are either or include interests, race, or people who share a common personality. The friends I make all share rather similar interests to me and are of the same age group/generation too, but my group is very multicultural. =]