I think I might be on to somethin. This might not mean anythin but first off, something I noticed was that with all three of the top ranked people in Organization XIII their name all begin with an X as does Xion. Now for the main part. I think Zexion has something to do with Xion. The first thing I noticed was that Xion is the end of his name. Second was that Zexion was one of the members of the Organization planning to overthrow it. If you read Zexion's section on this page (Organization XIII - Wikipedia, the free encyclopedia) it says how Zexion uses his power of Illusion to mimic others weapons disguise himself and make duplicates of himself which could be why Xion is seen holding a keyblade and why riku thinks it is fake. If you remember Zexion made a replica of riku in Chains of Memories.This quote from the same web page backs up my theory "Zexion's weapon and powers were unknown because he had died without fighting. Because Nomura was unsure if it would be revealed later, he kept information about it secret. The development team also destroyed his gravestone in the World That Never Was that would have shown his weapon." Now for the final point, I THINK XION IS A CLONE OF ZEXION, maybe with looks altered or even a girl version of himself, who has been left behind after the real Zexions death to beat the organization by being on the inside. The plan of the organization is to obtain hearts which sora does for them by killing heartless, but I think the reason Zexion wanted to betray Marluxia and stop him from using Sora is because he wanted to gather sora's data so he could turn into him or make a replica and obtain hearts on his own without the real Sora. If you look at a picture of Zexion he does look quite like a girl. This could also explain why Xion isn't actually a nobody and wasn't properly included in the organization. In chains of memories axel persuades the riku replica to kill Zexion maybe this is so he cannot harm sora because he "cares" about roxas who is part of sora, note that this happens after sora has killed Marluxia so nobody would know if Zexion created a replica of himself.
There all done lol.
There all done lol.
