Kingdom Hearts II So what's up between Naminé and Kairi?

I don't know if I'm wrong but I have to ask.

First of all in KHII Roxas is half of Sora and Sora isn't whole until Roxas is in him. So if Naminé is supposed to be Kairi's half, Kairi ain't whole during the entire game? I mean cause Kairi is supposed to become a kind of heartless in KH1. And why does Naminé has those powers of the memories and that stuff, if Roxas can wield the keyblade because of Sora...then Naminé have those powers because of Kairi?

 

Kairi was a Princess of Heart, so any nobody of hers would be extremely special. Kairi is apparently not whole without Namine, and so how she is walking around without her other half, while Sora couldn't wake up without Roxas is a mystery to me. Maybe, again, because her heart is pretty strong?

 

Maybe it's cause the writers were too lazy to come up with some characterization and story for Kairi so they just gave her Namine as a nobody as a way to make her "special". The reason for Namine being Kairi's nobody was so convoluted and unessesarily complicated. With Sora, it was pretty simple. He was an actual heartless(the monster) at some point and he got Roxas as a result.

 

I think most of that's going to be explained in one of the new games. I mean, there's Namine, Kairi, and now Xion (is Xion also Kairi's nobody? I think that's what they're implying in the trailers I've seen).