put in order oldest to youngest meber.

I don't think there's any way to be 100 percent sure on this one, but I always thought it was something like this: Vexen, Lexaeus, Xaldin, Xigbar, Xemnas, Luxord, Marluxia, Saïx, Axel, Larxene, Zexion, Demyx, Roxas, Xion. :P I dunno, hope that helped.