14th member theory:

I'll read it when i get a chance.

Unbirths became existent after bbs.

Okay a keyblade becoming an unbirths would that mean all keyblades can become unbirths i doubt it. Next that would mean that Xion would be number 13 if im not mistaken because Xigbar is later on talking to Zexion and tells him that they recruited a new member Marluxia number 12. Another point is that Xemnas is connected to MX in some way or form im sure that Xemnas doesnt have memories of before Ansem the wise found him.

I can explain this on the next quote...Xion isnt a keyblade.

Let me explain this riku split his way to dawn and gave it to kairi his way to dawn changing form is unconfirmed but riku gave kairi his way to dawn and he duel wielded which would mean that kairi wasnt actually wielding the keyblade riku wielded for her.

Probably because she disobeyed the organization and got erased.

It was his own keyblade.

Xion is affected by soras memories.

Oh heres something that you would like to know xion doesnt meets the requirements of the organization.

It is explained that when a persons body and soul becomes a nobody that slight changes to their appearance occurs.