I disagree with the premise that Rumpel is the center of most of the fairytales. I don’t think he is at all. I am not sure why Rumpel wants the children though i don’t think he wanted Cinderella’s child to give to Belle. I think the deal with Cinderella was more of an afterthought and was not planned out. He just happened to be there to kill the fairy godmother and take her wand and Cinderella wanted to do a deal.