I just realised that I have seen 'Another side, Another story', but have not seen Deep Dive. I don't think KH-Final Mix is going to be released here, and I didn't even know Deep Dive existed.
After looking at that site, the ending of Kingdom Hearts has alot of speciulation. My guess is that the two people are two new people, maybe variations of the same person. I don't think they could be Sora, as Sora has longer hair, unless he cut it. Also, we see Sora in two different shots in Deep Dive. You also said that it can't be Riku.
I honestly think that there isn't enough information to pinpoint who the two unkowns are. We'll justhave to wait until KH2.
