So where did this kid come from?

I'm still trying to figure out where my 5th child came from. No, no, I understand "how that works" ;) What I wonder at, is how he is so different from my other children, especially the middle two. This morning, for instance... While Ryan (4) and Amanda (3) were sitting and standing on either side of me in the bed this morning, singing and talking loudly while I was desperately trying to get a few more minutes sleep, Ethan (22 months) was still sound asleep in his crib across the room from us. (And when he does wake up, he will often just quietly play with his toys in the crib for a while before climbing out to find me.) While Ryan and Amanda were climbing into my windowsill a little while later and jumping off onto my bed (I was up by then!), Ethan was sitting quietly at the dining table eating Cheerios. While Ryan and Amanda were downstairs loudly watching and arguing over cartoons, Ethan was lying on my bed, blanket over his legs, "reading" a book out loud. I just don't know where he came from...but I'm hoping our new little "Peanut" is a lot like him. :)