Yes, I know exactly what you mean! I had a character named Jordan, Harry's son in a next-gen story. Lovely boy, really. His twin sister was very outgoing and excitable, so I made Jordan more quiet and bookish, the less dominant twin. He was a bit of a wimp, I guess-- his sister would drag him into mischief, although he was very goody-goody and didn't like getting in trouble. But he was a nice kid.
Do you ever find that your characters start to boss you around? Have you ever started writing a story with specific intentions, but your characters refuse to cooperate?
I have often found that characters I write take on a life of their own. They do things I don't want them to do, and take on character traits I never intended for them. Quite often a story will come out completely different to how I originally planned it, simply because one or more of the characters had a will of their own.
So, does this happen to anyone else, or am I just crazy?