We are having problems with our son, 3 years old (38 months) and our daughter, 19 months, fighting. Our son can be very aggressive with her and has recently increased in physical aggression towards her. She is also aggressive at times and does sometimes provoke him. She can be quite dramatic when she is hurt, (even very minor bumps), whether by her brother or just from falling, bumping her head, etc. I try to let them "figure it out" regarding sharing and playing together. I am having a hard time lately because my daughter will start crying at being hurt and I haven't seen what happened...often I suspect that my son has hit, pushed, etc. but didn't witness the incident. He is not forthcoming with information, I think even lying about it, and she can't speak well enough to tell me what happened. If I suspect that he has done something, but am not sure, should I still punish him? (I am adopting a no tolerance policy for physical aggression from him and will be putting him in his room for the remainder of the day for any occurrence.) I am also concerned that she is becoming the "victim" and him the "bully" but don't know how to stop that at this point as he is a bully to her regularly.