[jhein]

I don't think you're wrong. A 6 year age difference, and even 4 year difference at that age range is a lot, especially when it comes to physical games and sports. The 13 year old is hitting puberty so that's a problem, especially if he is defiant and dismissive when you try to talk to him. If that's his attitude and he won't change it then you could not allow your daughter to play with him in any kind of sports or rough games. But his defiance is the concerning thing. Maybe try having his mom talk to him. Complicated situation so good luck with it.