okay, ill go all out on this one. First and foremost, when we first meet Axel, he is "seemingly" alied with Marluxia. The first clue to Axel's connection with Sora, is his mention of Sora's bout with the darkness. He says that Sora is the only person to ever become a heartless, and still contain his heart. With the exception of one.
Now here's where my first theory comes in. I think that it is possible that Axel is the other person. Perhaps Axel was once a Keyblade Master himself, but he was beaten by the darkness, and recruited by the organization. Then, once Marluxia proposed the rebelion, Axel saw it as his time to retake his old life....or...somthing.
After their first battle, Axel had seen Sora's potential, perhaps, Axel really did see a bit of himself in Sora. And then, devised his true plan, he would release Namine, and from there, let the peices fall into place. Its my guess that he predicted Marluxia would "pull a fast one on him" and force him to fight Sora. Axel used this to his advantage by not only covering his foot steps by telling Marluxia that he was a spy from the Organization, but by faking his own death as well. This way, if Sora could not defeat Marluxia, Marluxia would still have no evidence against him to report to the Superior. (Even though Marluxia was rebeling, the Superior did not know this, as we learned from that conversation between the basement unknown)
So, when Marluxia was defeated, Axel saw it safe to start taking out the Organization members, one by one. Seeing as the all the people who had evidence against him, either thought he was dead, or were dead themselves. Now, Im guessing that Axel will be, perhaps, a reluctant partner to Sora, seeing as their motives are the same. To destroy the Organization, for what ever reason.
So, that enough for ya?
(I did it again didnt I?)
