xiii is the roman numeral for thirteen and their names are anagrams of their Somebodies name with an X added. For example: R O X A S = Sora with an X added.
I've compiled a list of what i reckon/know their sombodies name
Xemnas=Xehanort pretending to be Ansem the wise X E M N A S = Ansem
Xigbar=Braig
Xaldin=Dilan
Vexen=Even
Lexaeus=Aeleus
Zexion=Ienzo
Saix=?
Axel=Lea (pronounced L E E)
Demyx=Dyme
Luxord=Durlo
Marluxia=?
Larxene=Arlene
Roxas=Sora
Xion=?
The members of Organization XIII are:XemnasXigbarXaldinVexenLexaeusZexionSaïxAxelDemyxLuxordMarluxiaLarxeneRoxasXion~By MapleLeaf~
it is still called organization xiii
To show his loyalty to Xemnas and Organization XIII, the 'X' symbolizing the fact that he has no heart. His somebody is Isa, who does not have the distinct scar, meaning it has only been there since after he became a Nobody and was recruited by Organization XIII. Either this or it is the result of an injury which has left his face scarred.
No, Riku was never in Organization XIII. He wore the cloak because he wanted to hide the darkness in his heart.
lexaeus
Organization XIII's members definitely existed at this point, but the name 'Organization XIII' probably wasn't created until the time of Kingdom Hearts Chain of Memories when Roxas joined, making thirteen members altogether. We know, because of the events in Kingdom Hearts Birth by Sleep, that the members of the organization were mobilized, but "Organization XIII" in specific might not have been established.
The eldest member of the Organization is Vexen, the Chilly Academic.
The human forms of Organization XIII's members appear in Kingdom Hearts: Birth by Sleep for the PSP.
Zexion has no meaning in the Japanese language as it's origin is entirely English.The understanding behind the Organization XIII nobody names is that they are scrambled forms of their original (non-nobody) names, with the addition of X.Spoilers:As such, "Roxas" is just "Sora" with an X added. Similarly, "Zexion" is actually "Ienzo" with an added X.This applies to all Organization XIII members save for Xion, who is neither a nobody or Organization XIII member.
The birthday 10 13 2008 in Roman numerals is X XIII MMVIII.
Organization XIII might have used it as a home base to regroup, rest, and practice in the case of Kingdom Hearts 358/2 Days.
Zexion is Organization XIII's Number VI The Cloak Schemer