Ok I just found out something awesome. Well, it might not be that awesome but, I now know the name of the 14th Member in the Organization. The name's Xion and it's confirmed.
Though the mystery revolves around that girl is the key point of the game. So KH fans out there, if you really want to crack the extraordinary story of Kingdom Hearts into deeper parts, I recommend buying a refurbished DS and import 358/2 days game. LOL