There have been studies done on the impact of birth order on children's personalities. I haven't read them, but people have told me (so it must be true). I've been told that eldest children are pleasers and rule followers, second children are comedians and if a third child is the first of their gender, they'll be a pleaser too.
So I offer a small piece of my morning as utterly useless anecdata:
The two boys are upstairs playing trains. Screeching breaks out, with clear indications that Ben is screaming at Charlie for breaking the train track. Elissa is downstairs. When the yelling starts, she looks up at the ceiling and says, "What's wrong with Ben?". "He's yelling, isn't he?", says I and she furrows her brow and says "I'm going up there."
Up she goes, and 5 minutes later they all come downstairs happy.
Ben: aged nearly 7, rule follower extraordinaire
Charlie: aged 4, source of chaos and comedy
Elissa: aged very nearly 2, peacemaker