i have read a lot of conflicting opinions on this
a lot of people say 2 boys might fight but i have also read that 2 girls can fight (each trying to be the alpha female)
as long as you get them spayed and neutered, i think a boy and a girl would be good
i have 2 boys and 1 girl...the boys play with each other the most and i have never seen any aggression or fighting between any of them