Bad temper

When Hong Zheng asked for somthing and i refuse, his first reaction will be giving me a hit. Actually i do not hit him in most of the time and i would say rarely but why he behaves in this manner? I really do not understand. How can i help him? Sister told me this is "Karma". WE cannot change much and just modulate it. I hope i can teach him slowly and step by step and i believe he will change to be a better person under my love and care. I strongly believe.