How many members are in Organization XIII

starts at thirteen then drops to two
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In kingdom hearts 2, there are just 13 members they mention. In kingdom hearts 358/2 days there are 14 members:

1-Xemnas
2-Xibar
3-Xaldin
4-Vexen
5-Lexaeus
6-Zexion
7-Saix
8-Axel
9-Demyx
10-Luxord
11-Marluxia
12-Larxine
13-Roxas
14-Xion