Hmm.... I thought there is one as a Org.13 member and one that shouldnt have exist.
Though answered, I'll elaborate a bit
The reason Roxas didn't remember Axel was that DiZ - probably through Namine - altered his Memories so he wouldn't remember being in the Organization, thus making it easier to keep him locked up in the Digital Twilight Town - he didn't remember he had to escape.
Roxas "shouldn't have existed" in general for he is a Nobody, and Nobodies aren't that much of a natural occurence. The "Existence" is the Heart - Sora. "Organization Roxas" and "Twilight Roxas" are one and the same, minus his Memories of being in the Organization.
On a side note, it makes me giggle, seeing how Roxas
can't Exist for he is a Nobody. Saying he
shouldn't have is, in a way, saying that he does, in fact,
have his own Existence...
Though that'd go nicely with the FM+ scene in which
Axel asks Roxas if he has a Heart of his own
Hm...