I believe I read in the latest PSM that the battle system for Kingdom Hearts will be that you control the main character, Sora, and while the AI controls the other two members in your party. The reason why you can't control all three, is because, occasionally, there'll be some Disney characters that will come join you for a short period of time, then they'll return and you're back with your two original characters. I hope that made sense. I think the two main sidekicks of Sora's will be Goofy and Donald.