Why do people find it attractive when two girls kiss, but not two guys? any science behind this?

Great question: I've wondered about this. Perhaps it is a part of male dominance in general. I doubt there is any basic science behind it but i'll be really interested in any answers you get.

Based on gender pref: "people" can find various combos attractive. May be based on your gender/sexual preference. Hetero males often find 2 females together stimulating, maybe due to imagining oneself w them (whether consciously aware of it or not). Gay males may find 2 men stimulating. I've known teen females who were obsessed w male-male pairing. Depends on what floats your boat. Not scientific, just my observations.