My fiancés little 9 year old boy cousin is sleeping in our room until he gets his own room. Well he…

My fiancés little 9 year old boy cousin is sleeping in our room until he gets his own room. Well he has been so bad this whole time. He's mean to our 4 year old daughter when she does t want to play what he wants to play and when he gets caught being bad and you try to some what punish him he starts hysterically crying and then after that he just gives me a dirty look.