(Spoilers) I think I know how to distinguish between Roxas and Ventus now.

[SuperSaiyanSora]

Yeah i wonder, if Project Xehanort will explain how Eraqus went from looking at most 5 years younger to looking at least a decade or two younger.

Thanks to ReMind we know the one that doesn't look his age is Eraqus. The dude does not look like a teen + 64 years in BBS.

It could also be a matter of either Eraqus being much healthier or Xehanort's tinkering with darkness over most of his lifetime had an effect on how much his body's aged. In BBS, I thought they were around the same age and Xehanort just didn't have good genes on his side... But in KH3 when they're playing chess, they look to be about the same age.

 

[AdrianXXII]

It could also be a matter of either Eraqus being much healthier or Xehanort's tinkering with darkness over most of his lifetime had an effect on how much his body's aged. In BBS, I thought they were around the same age and Xehanort just didn't have good genes on his side... But in KH3 when they're playing chess, they look to be about the same age.

Spoiler Show

I could believe Xehanort to be an ungracefully aged man in his 50s or 60s, but i can't believe Eraqus being a gracefully aged man in his 80s. With the chess scene taking place approximately 65 years before bbs, Eraqus would have to be at least 78 years old.

Maybe light just has amazing age slowing properties or the Land of Departure is in a slower time flow.

 

[SuperSaiyanSora]

Spoiler Show

I could believe Xehanort to be an ungracefully aged man in his 50s or 60s, but i can't believe Eraqus being a gracefully aged man in his 80s. With the chess scene taking place approximately 65 years before bbs, Eraqus would have to be at least 78 years old.

Maybe light just has amazing age slowing properties or the Land of Departure is in a slower time flow.

Spoiler Show

I think you're right. It's gotta be either one of the two. Disney worlds seem to have their own time-related properties and how time might flow, so maybe that's the same for the Land of Departure. Plus LoD seems to be related to Scala ad Caelum in some way. Light could also be it too because it's been implied that darkness can corrupt if you're not careful. So far, it's been shown as a corrosive force of nature, so maybe that's what happened with Xehanort in the time he was learning to control it.

Xehanort didn't need the black coat anymore, just like what the MoM said, but Xehanort wasn't always that strong.

 

[cakito123]

The real question is Why didn't ventus age when he was sleeping inside castle oblivion? Like, Sora did age when Namine was restoring his memories, so in KH every character should age anyway, sleeping or not haha

Maybe because Aqua's magic have a different power I dunno

 

[SweetYetSalty]

The real question is Why didn't ventus age when he was sleeping inside castle oblivion? Like, Sora did age when Namine was restoring his memories, so in KH every character should age anyway, sleeping or not haha

Maybe because Aqua's magic have a different power I dunno

Ventus has eternal youth! I'm calling it. Hasn't aged since the fairy tale age, hasn't aged while asleep for a decade. Old man Xehanort wishes he had this ability. That's the real reason he wanted Ventus at first. That's my theory and I'm sticking with it.

 

[Noivern]

The real question is Why didn't ventus age when he was sleeping inside castle oblivion? Like, Sora did age when Namine was restoring his memories, so in KH every character should age anyway, sleeping or not haha

Maybe because Aqua's magic have a different power I dunno

Because what was resting in CO was his body, while his heart was hanging around in the Sora Hotel. It's already been stablished that the Heart pretty much shapes those things in the KH universe.
re: Xehanort's heart altered Terra's body to look similar to himself (silver hair, darker skin), Ventus heart going into Sora's empty body caused his Nobody to look like him, also the hearts of everyone using a replica in KH3 were what shaped the empty husks into their physical forms.

As for the whole "Xehanort looks too old while Eraqus is too young", older Eraqus is clearly a Japanese man while Xehanort looks like a typical western man. It's somewhat stereotypical, yeah, but asian folk do tend to age better compared to westerners, and while Xehanort is probably an Islander, I don't think he's actually racially coded as one past his skin tone, lol

Plus, while Eraqus has those scars of unknow origins, we know he has spent at least the last 10 years or so teaching at Land of Departure, but it's likely that he's been there for longer. We have no idea where Xehanort spent his last years before BBS or even where exactly he lived when he wasn't beating up young kids in the Keyblade Graveyard,
Living in a peaceful, healthy place and living in harmony as a teacher definitely treats your body better than hanging out in a desert and going through corridors of darkness all the time.

 

[Hirokey123]

Xehanort looks older because Xehanort has been experiencing different time axis for a long time as he travels worlds. Meanwhile Eraqus has sat in LoD with no indication he ever left it, so he's only experienced one time axis all this time. Very likely an axis that runs much slower than the worlds in the realm of light do because LoD was smack between the realm of light and dark. We know in the realm of darkness time flows much slower and in some spots not at all compared to the realm of light, so a world between the two most certainly has a time axis somewhere between. (which btw explains how Sora's handful of hours in CO translated to almost a month's worth of time relative to other things)

So while Eraqus was sitting in a single world, the ages passing more slowly for him. Xehanort was out adventuring, seeking, trying to find answers amongst the countless worlds experience different time axis some a little faster than others and over the course of 60 years that added up. I always figured that's what happened to Riku as well, Sora and Kairi aged only a little bit by about a year meanwhile Riku it looks like 2-4 years passed for him.

This is also what happened with Aqua and Terra who were practically the same age, the slow time kept Aqua young while Terra's body aged well into 30. Of course since Terra's heart was locked in a dark stasis, imprisoned, unchanging, it didn't really matter because Terra's body matched the form his heart remembered himself having just like all bodies do. So conveniently even though he is almost certainly 10+ years older physically, we won't ever see that because that's now how Terra's heart remembers himself, which is convenient for the modelers.