Mk, so Xemnas, since he became a heartless, which was give or take ten years ago (even though he was found later with no memories by ansem, so probably less) has been gathering up more members for his orginization, even during KH I cause he mentions maleficent having always been his pawn. And he found these other members with the help of the other 6 (or was it 5) pupils of ansem. And before that, well just refer to the ansem reports in KHI (not KHII, those are the real ones, the ones in KHI were written by Xehanort). And then there is always the possibilty that he becomes a heartless in BBS and the guy Ansem found already was Xehanort's heeartless.
And mickey, well he's been training with yen sid since ten years ago, and probably more, has built disney castle around that huge glowing thing (haha, can't remember what it's called), and has been ruling until KHI when probably alike a day or week before it starts he disappears, going off to find ansem because the "stars are slowly disappearing from the sky". And then during KHI you just assume he was looking around for ansem, got caught with his shorts down, and ended up in the shadows, porbably wandering around but still having his wits about him to find the way out. And then he runs into riku and closes the door to kingdom hearts, and thus we begin our journey into chain of memories.
Yeah, so hope this helps. And if anything i said is incorrect, let me know.
