Keep things safe. One important thing is for families to have clear rules about hurtful behavior. It should not be allowed. You need to take a more active role in teaching and limit setting. Your children may be developing very bad habits.
Sibling rivalry. We all know innocent sibling rivalry exists. But when it gets to a point where there is either physical or emotional concerns then one should be worried. I don't know ages of your children, if they are old enough, you can sit and have a talk with them, either alone or together.
Behavior probs. With raising our kids, we did not tolerate any behavior if it crossed the line and became violent. I published a book on kindle called parenting the kids according to a child psychiatrist which could really help you. I suggest doing whatever it takes, to stop the violence, if it is going on in your home. We never used physical punishments with our kids.