Two sons here Hans and it's always something between them. Mine are four years apart but still fight all the time. I've got a daughter in the middle too.
I just have never allowed the oldest son to ever hit either sibling. One rule I have always enforced and one that he has never broke because he knows what I'll do to him!
This has saved me a lot of aggravation because me and my brother fought every day when I was growing up and I remember getting yelled at and whipped all the time.
