I have 2 boys and a girl. My eldest two play really beautifully together for alot of the day. They do have fights, mostly for attention and because one has taken the others whatever. I think them playing nicely has more to do with the fact that DD is dominant and DS1 will follow her anywhere, he is so in love with her! So DD is happy someone is doing what she tells them and DS1 is just happy to be where DD is, lol. DS2 is tiny so doesn't do anything at the mo, though DD loves to play with him under his play gym and will chat and sing to him if he's on the floor.