So Xehanort diffuses himself into 13 incarnations a la Voldemort and Sephiroth. But wait, we're not talking about Xehanort.
We could have a Kairi game that focuses on her incarnations. Young Kairi, KH2 Kairi, Namine (her Nobody), Xion (a doll resembling Kairi due to Roxas having Sora's memories), and Aqua (who KIC'd Kairi).
The thing about girls in KH is that just like in Naruto, they're outnumbered two-to-one. So while there may in fact be 13 versions of Sora
(Sorganization 13) Valor, Wisdom, Master, Vanitas, AF Sora, Final, Young Sora, Digital Sora, Roxas, Ventus, Lion-Sora?, (hell, even Xion could work here too as Xigbar saw it as Ventus and Xemnas saw it as Sora), ... lol so obviously grasping at straws to reach this number... and
RikuYoung Riku, Dark Riku, Riku Ansem, Riku Replica, Axel, Terra, Data-Riku, etc. to equal Xehanort's, there aren't as many versions of Kairi.. unless we decided Larxene was somehow a version too. lol