Simply put: there's always an exception.

Unnecessary explanation that is not to be read unless you can both understand and accept this
I could try to explain this, then be wrong. I could shy away from the subject, and appear foolish. However, if I had bothered to listen to my Literature teacher, then I would know that the friendship between Axel and Roxas is a literary device, used purely to create entertainment and keep people guessing.

Even the OXIII knew about this friendship, but it can't be explained. Since Axel is the closest Nobody to ever have regained his humanity (which he still failed to do), it's not a far cry to assume that he can replicate true emotions. Which came first? The friendship or a disposition toward regaining that which was lost? The answer to either of these is a completely different way of looking at Axel's differences from the other members.

If you look at it from Roxas' side, it doesn't quite seem that he holds Axel as closely as he wants to know. This is further explored in FM+, where he calls Axel "partner," not friend, but Axel begins to cry as Roxas fades away.

To look at the relationship as though it had anything to do with Sora still existing, would be false. Nobodies are a completely new entity from life, and they usually have their old memories. To remember that Roxas is an exception to most of the rules would be of utmost wisdom. You'd be surprised how quickly you can make friends if you have no memories.


Memory is not half of emotion. Memory (in terms of experiences) is 100% of identity. Your past makes you who you are, not how you will react. Nobodies do not have an identity, since they are not people. Additionally, whether or not a Nobody has their other half in existence is irrelevant to whether or not they can have feelings. It just simply does not matter.