illegal defense

[EMM]

I am not complaining, I am just trying to understand if there is a rule or not regarding this type of double and triple team coverage. The reason I am asking is because the refs are often selectively enforcing the rules(travels, carrys, double dribbles, reaches, etc). Things are very political in my league unfortunately and I am just trying to make sure my kids are treated fairly. It seems that the refs allow the other kids to really rough the big guy up, and then when he is going for rebounds they call over the top all the time even if it is borderline, which almost always puts him in foul trouble. I have taught him to pivot and use the backboard effectively, something that is prior coaches failed to do.