another one bites the hand, another one bites the arm

I was watching a couple of our friends kids this week and the two girls were playing and wouldn't let the boy play with them so the boy decided to grab Alexandra's hand, stick it in his mouth and bite down. Two days later, Alexandra and Sebastian were wrestling on the floor and Alexandra comes into the kitchen crying. Sebastian bit her in the arm. I'm making an official rule right now, no more boys biting my daughter under my roof!