By and large they're pretty tough with each other, but not dangerously so. However, every now and then, if Buckley gets tired of wrestling before Jellybean he'll let out one of those ear-grating protests that makes it clear this isn't fun anymore. And if Jellybean, being the older brother, doesn't take the hint, Buckley gets louder and his tail hair sticks straight out, making it look twice as big. I always used to think this phenomenon was strictly the property of cartoons, but it's not. Real cats get fat tails when they're angry.
When I get angry, I get kind of stiff. I used to think I had a pretty good poker face, but the responses I've received over the years tell a different story. I'm not sure what exactly it looks like but I think it involves narrow eyes, a hard jaw and red death-rays shooting from my pupils.
One thing that doesn't happen is my tail-end doubling in size, and for that I am grateful. It would probably be a serious motivator to become a peace-filled person, but all the same I'd rather give up on anger for less physical reasons.
Oh, and I'm also grateful that when people make up, no licking of other persons is involved. Try looking your siblings in the eye after that.