Sorry, I didn't make myself clear on that point. Like Hirokey said, I meant some form of time travel, not necessarily time travel itself like Xehanort does. Maybe it's connected to the dream worlds / sleeping worlds, but it is a form of time travel for me if a character is present in the age of fairy tales and 100 years later also because he / she is traversing through time in a way. I'd love the three original Ux characters take the main focus of attention, that would be nice.
By the way, I am not sure if the realm of sleep would be a logical explanation. The chamber of waking is already bothering me since Ventus doesn't age - Sora fell into a similar coma and DID age so CO doesn't prevent aging. Just because the chamber of waking cannot be accessed by someone else than Aqua, that doesn't mean it is unaffected by time. A heart can sustain for a while without a body, but a body without a heart should still age (best example are the Organisation members).
I always suspected that the sleeping realm is some kind of time loop (I didn't find DDD very clear on this point), but how do you end up there and - better question - how do you get out? Why do you get amnesia from that (as we see in BBS)? (No really, I can't explain that in a way that makes sense, fill me in.)
I'd stress that you consider this theory that I created. It's plausible enough to explain how pre-existing characters exist in this era.
https://forums.khinsider.com/kingdo...sule-theory-5th-union-leader-explanation.html
A lot of people who are baffled by Ventus and Lauriam's inclusion in this game are under the assumption that they went from the present to the past. However, if you believe that both these characters originated from The Age of Fairy Tales, then the puzzle isn't why they were able to time travel to the past, but rather, how they survived beyond The Age of Fairy Tales.