My 7 year old son is the middle child- he has an older brother who is 9years and a younger sister who is 4. I have reached my wits end with his mean behaviour. He is always deliberately mean to his siblings. We have tried the reward system of allowing him to play on the Wii or his DS. But it has reached a point where he has lost almost all his privileges. And he seems to show no remorse for his behaviour. Someday please help me understand what where I am going wrong in helping my child grow into a decent human being.

How is he with other kids at school?
When did this start, if you can recall?
I'm not one to suggest doctors easily, but he may have a deeper problem either physiologically (brain chemistry, testosterone, etc) or emotionally, such as one seemingly small incident of favoritism toward his sister or of teasing by his brother that had a huge effect on him. I'd try the psych consult first.

What punishment is used, taking away use of things? A swat to the rear? Loss of activities?