I mean he could be someone else or the enemy after the xehanort saga, but look at him. He has two blades like xemnas and sort of fights like him too. He also does the X-blade move that vanitas does. Maybe he(they) went back it time to try and kill them and change the future to their liking(them ruling the worlds) but as you can see he(they) failed and had to run back to the future. What do you guys think?