I'm sure it's been discussed before, but what chance is it that it could be Xehanort? I mean the both have Silver hair, and an affinity (and greater control than most) for the power of Darkness, strong hearts chosen by the Keyblade, both wanted to escape the islands... If nothing else, I'd say that they're at least related (I'm sure silver hair isn't too common a genetic trait in their small island community)