wow ur theory is really good! And there are obviously still heartless in the worlds right? Because of when Kingdom Hearts exploded, all of the heartless came back. But the only question is about Maleficent and Pete... They HAVE to be in KH3..unless they died while fighting all of those heartless. Did everyone forget about them? There is still some sort of evil in the world and it being the Souls of our former enemies makes complete sense.
There's only one thing... Isn't a nobody the body AND soul?..
There's only one thing... Isn't a nobody the body AND soul?..