My 3 year old has started biting his younger brother who is 2 years old. He bites him on arm or hand almost everyday. I do time outs of 3 minutes in the hallway for his punishment but he doesn't seem to get it. My MIL told me to try biting his hand so he knows it hurts. Is biting something he will grow out of or something I will need to constantly be punishing him for on a daily basis?