confused-roxas & Sora-Kairi & Namine-???

Question

How are they the other one of them and like
roxas is sora's nobody and
namine is kairi's nobody

Answer 1

Yes, Roxas is Sora's nobody and Namine is Kairi's nobody.

In the first game Kairi is attacked by the heartless and her heart remains safe inside of Sora (night they were attacked in the secret spot) Creation of Namine.

Sora released Kairi's heart from him, causing him to become a heartless. Kairi helped him, and he was no longer a heartless and then Roxas was created.