Well... i was reading through past Nomura's interviews and i found out this one:
Now, remember that we learnt our memories resides in our hearts in the KH-verse.
So i realized that the Ansem The Wise we saw in the Realm of Darkness talking with Aqua is instead his Nobody.
He just lost his heart due to the heart-machine's explosion and then his heart was gathered by the Organization's Kingdom Hearts. His body, nobody to be exact, was swallowed by darkness and then he finished in the RoD.
After a while (we don't know how time flows in RoD, in fact we don't know if it even flows) Sora defeated Xemnas and freed all the hearts imprisoned in KH so his heart was returning to him and some memories just to reflow in his minds: otherwise it is not clear how he knews about Sora winning over Xemnas, it was actually considered dead. Now he need to return to the RoL (like Aqua) and then maybe use Namine's help to restore all his memories.
When the Heartless are defeated, what becomes of the stolen hearts? Also, when members of Organization XIII and other Nobodies are defeated, do they return to their original form?
When Heartless are defeated, essentially the owner's hearts are rejoined with their once extinguished body, whichever world it may be on. As for the whereabouts of hearts in KHII that turn up, this time they remarkably went to the Organization (there is a foot note here that says "In Kingdom Hearts II after Heartless were defeated, the many hearts were absorbed by the Kingdom Hearts of "people's hearts"). However, in the rare case that the body changed into a Nobody, when there is no container for the heart it resorts to a state of suspension.
In the case of a Nobody being defeated, it's a little more complicated. If the above mentioned hearts are liberated, they return to their original form. However, if the heart is still stolen by the Heartless, the Nobody's body is swallowed by darkness. If somewhere in the world their hearts are taken back, perhaps they might be able to return to their original human form.
Now, remember that we learnt our memories resides in our hearts in the KH-verse.
So i realized that the Ansem The Wise we saw in the Realm of Darkness talking with Aqua is instead his Nobody.
He just lost his heart due to the heart-machine's explosion and then his heart was gathered by the Organization's Kingdom Hearts. His body, nobody to be exact, was swallowed by darkness and then he finished in the RoD.
After a while (we don't know how time flows in RoD, in fact we don't know if it even flows) Sora defeated Xemnas and freed all the hearts imprisoned in KH so his heart was returning to him and some memories just to reflow in his minds: otherwise it is not clear how he knews about Sora winning over Xemnas, it was actually considered dead. Now he need to return to the RoL (like Aqua) and then maybe use Namine's help to restore all his memories.