Obviously I can't speak for you, but I can't say you don't have it. I have a brother who's about a year and a half older than me, and any time he's ever been in a fight, I get shaky.
I was in a bar one night with a friend, where we stopped in on the way to a party. After about a half hour he says, "Why are your hands shaking?"
I said, "I didn't realize they were. Usually when that happens, my brother's in a fight."
He dismissed it, until his cousin walked in about 15 minutes later and said, "Your brother just broke some guy's leg!"
My friend turned ghost white. It was hilarious.