Axel = Reno?

[PuPu]

Maybe Axel is Riku's nobody since Riku was once a heartless since Ansem took over his body and he had the heartless symbol on him and even then still in kH II he was in Heartless Xenahort's body, so maybe.

Doubtful, because if you mix up the letters and Riku and add an X, it's impossible to spell "Axel"

Whatever made you think this idea?

Most likely from the fact that Roxas and Axel are friends like Sora and Riku.