It's a picture book I remember reading as a child. I can't remember if he was referred to as Santa Claus, Kris Kringle or St. Nicholas. I remember it was about him as a little boy with blonde hair, and he would often go out to play in the snow. A house key was attached to his snow suit so he wouldn't lose it. He ends up losing it, (I believe his brothers locked him out) and goes down the chimney to get back in. I've searched and searched but I've had no luck! Anyone remember the title?