The white one's the boy, and the orange/white one is the girl.
I first said that by differentiating which picture was "on top," but my sentence phrasing came out very odd and I don't think they know each other that well yet. XD
Well, they were in the same fishtank, but they don't ever stay at the petstore for too long, so... I'm going to guess they've known another for three days, give or take.