not THAT important, but since they are actually giving us more story than the rest of ff characters, they hould at least explain it, try not to pass things to easily
Not really. There is no need for it. Cloud is from Radient Gardens. He got left behind when Cid, Leon, etc fled RG. He became a pawn of the darkness at a young age; 9-15. He may not have been able to escape on his own. Anyway, he was found by Maleficent, who gave him to Hades. Cloud may have lost his mind, and developed an alterego; or two. They were able to manifest in the real world, and only Cloud & off-worlders are able to see them.
There, Cloud backstory. No need to have it in future KH games because it's not important. Because if it was, it wouldn't be in a KH game. KH=/=FF. Two separate games; two separate universes. Cloud's backstory isn't important. Let it go.