Why didn't they call it the Organization XIV? (14) cause they where with 14 people

 

And its not because Xion died because in Kh2 half of the Organization ''died'' and the still called it 13.

(DS)

"One of us? Don't be absurd. Count the seats. When have we ever been more than thirteen?"

— Saïx talking to Roxas about Xion

 

(PS3)

"A puppet couldn't be part of the Organization. Just count the seats here. We have and always will be thirteen."

— Saïx talking to Roxas about Xion

 

Also when the X-Blade broke apart there were 7 pieces of Light and 13 of Darkness

 

Xemnas with Xehanort's thinking was OCD and wanted there to only be an official member per piece

 

This explains why the Organization really only limits themselves to 13 in the first place rather than creating a hundred or a thousand Xehanorts

Edited September 8, 201411 yr by Ruby Rose

Xion was not a nobody. She was a puppet like Repliku.

You kinda answered your own question,they are destined to be XIII members,it doesn't matter if half of them dies or if they add a an extra member,in the end Xehanort needs 13 people

Xion never really counted as an Organization member.

And also, when they were first called Organiztion XIII in KH2, it was when there really only were 13 members since Days was made after 2.

Mainly because they had already paid for the stationary watermarked with XIII, and to return it all and have them reprinted would just cost a lot of money, so they decided to stick with the original name.

Because Xemnas never intended to allow both Xion and Roxas to continue to co-exist. One was always supposed to absorb the other so by the time his plan was complete there would only be 13. There where only ever supposed to be 13 members.

Edited September 8, 201411 yr by Isamu_Kuno

Xion was supposed to absorb roxas and become a whole. 

There was never supposed to be more than 13. 

If you watch the scene where Xion arrives in DAYS, Vexon leans forward, grinning. 

He's observing his work in action.