>>712828654
Kris would probably be outright dead if his soul was stolen and he was a natural human. A Process Occurred at some point in his life no matter what to make him into a receptacle for unrelated souls, it seems much likelier to me from the phrasing of "human parts" and his status as a cage and all the recent developments surrounding a gray hand that he's a vessel (as in Gaster experiment) and always has been, right down to mysteriously being the only human in a monster city.