The issue is that I don't feel that just because Namine and Roxas' other halfs are a couple, automatically means they would be a couple as well. As both Mercen-X and I have pointed out, they barely know each other. Even if that was enough, I would argue their love is the same as their existence, fake. Cause they don't actually like each other cause they fell in love through their time together, instead they are compelled to be in love cause their bodies happen to be a couple. So I feel any relationship these two would have with just from the info from 358/2 and KH2 would make the two question their own feelings for each other, if that were the case.
Also, considering the revelations of BbS, I feel its safe to assume that Roxas should not be treated as simply being Sora's Nobody cause of extenuating circumstances and thus should be free from the idea of "if Sora likes it, Roxas likes it" and neither should Namine herself since she as well holds part of Sora within her due to the circumstances of her creation.
Its because of this that I can't really say Roxas should be with anyone, cause he has no real relationship with Namine, and Xion is just another part of him, and even then I would argue they are more friends or brother/sister in terms of relations to each other.
I think most people prefer the Roxas Xion pairing cause its more grounded, you actually get to see the two grow together and have adventures and free time. Whereas Roxas and Namine's time together in all the titles makes up less than 10 minutes. I just don't feel their is strong evidence to suggest they like each other in that way let alone be a couple. I still interpret the scene they have together at the end of KH2, as more of friendship than love, simply because the rest of the evidence in the game shows its not possible for them to have hooked up so quickly. I still feel their relationship is one more based on kinship than romantic interest cause both were able to merge back with their other halves and continue to exist.
