Oh look a chance to spill my "Axel is Riku's Nobody" theory in all its grand holes!

I think Axel comes from Riku because Riku did not truly become a heartless but also lots his heart...Uh, sort of and such. I'm talking about when Ansem took him over and he dived into the darkness completely. Similar to the way Kairi is somewhat special in the way her Nobody was created. Kairi's Nobody is Namine, but their hair color does not match and they have somewhat different features. Since Riku lost his heart then reclaimed it, I think Axel is also a 'special Nobody' and so he has differnet features from Riku. It would also explain his connection to Roxas. Since Roxas is Sora's nobody he may have unnaturally high feelings of friendship because of that. Of course, being a member of Organization XIII his name is supposed to be a scramble with an X so I'll just explain that away with "faked it".

Well enough of my flawed logic. Let's all just agree that Saix is Kimahri's Nobody.