Don't hit him it is not his fault. I understand it could be frustrating but why is he acting out? I agree with others that posted in that his mother is at fault. You should have it out with her and find out how you could help him. Perhaps trying to find a way to communicate with him or get someone that he would open up with. A child at his age that is not affected by being hit may have been hit a little too much. and has just gotten used to it. If all fails, just stop letting her pawn him off on you. I wish you the best..