I don't know how or when it started, but it ended today with a branch swung at a face. And I realized it was time to do something serious.
There is a mindset that "boys will be boys," or that boys are naturally more physical, but I believe as a parent it is my job to help shape my children's character, and anger and unkindness are two things I want them to conquer sooner rather than later.
Squabbles usually end when Caleb lashes out by hitting, striking, pushing, etc. That's when I jump in and separate the parties, reprimand Caleb for "using his body" to express his anger, and impose a consequence or punishment.
Caleb naturally gets physical when he gets angry. He is such a sweet soul for the most part, and when he lashes out right now, it's done without thinking. He is usually in tears, complaining about the (non-physical) actions of the other person. I try and try to help him understand that although the teasing or other behaviour that led to him hitting someone is also inappropriate, the physical reaction can have long-lasting effects like scarring, stitches, broken bones, or worse.
Today, as I sat with Colin and his bruised face, my mothering instinct realized that while Caleb's reactions are wrong, there are always plenty of warning signs before he snaps. One of the boys is teasing him, or not playing fair, and Caleb complains "Stop! Don't! Listen!" over and over again. And so I turned to Colin and explained as much to him. I told him that from now on, if Caleb was disciplined for hitting as a result of Colin's behaviour, Colin would share in the consequence also. He was shocked at first, and sulked for at least an hour after. But building character goes down many roads, with many different roadblocks. Just because Colin doesn't hit other doesn't mean there isn't behaviours to be modified.
More than anything I want my boys to treat each other with respect. With this form of shared discipline (even for different behaviours) they can take responsibility for their relationship with each other.