While I'm sure that sisters have a "thing" that they do, I'm not sure what it is. And, I'm sure brother-sister siblings do, too. Again, I'm not sure what it is since I have no siblings myself, and I'm a mother to only boys. (DUH, you already knew that!)
Anyway. What brothers do is fight. Not like argue (though they do that too!) but wrestle. Most everything becomes physical. In my boys case, it's not just because they are angry or upset, but because that is just what they DO.
For example. Take a pleasant day in a public place. This didn't escalate, no one was hurt and there was no crying. BUT, there was a little bit of rough housing. It was all in good fun and both parties seemed to be amused by it, if not derived some enjoyment from it.
{here's where it begins. it looks as though sawyer started it, yet cam is participating}
{cam doesn't seem bothered or happy with it}
{cam's starting to enjoy it}

{the end. and thankfully, everyone is happy}
Brothers, not a bad thing to be.