[SPOILERS] Theory on the gray haired boy

[SeaSalt]

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i swear if Nomura pulls some bullshit
"Oh yeah this Xehanort is a castaway and the original Xehanort before he split himself in half and after that the dark side of Xehanort went on to disastrous things while sending the Good Xehanort to the ROS to not interfere and blablablablabla i will be done with this garbage for kid. I'll throw every KH out the window

i actually could see this happening, because we need a reason as to why he's that age and why he's in the RoS, since MX has grown to be an old man by this point...

 

[Sephiroth0812]

i actually could see this happening, because we need a reason as to why he's that age and why he's in the RoS, since MX has grown to be an old man by this point...

The age could be an effect of the Realm of sleep though: Look at Sora and Riku.
Another possibility of Xehanort looking that young could also have to do with Vanitas, it does not have to be the seventh(eighth?) form of Xehanort.
(Seriously, does Xehanort want to build a soccer team?).

 

[SeaSalt]

(Seriously, does Xehanort want to build a soccer team?).

yeah, didnt you hear about the KH olympics? XD

but seriously, even if it was the RoS that changed him he really does have features of other characters, like riku for example.

and vanitas is in there, with the same appearance, meaning he hasnt aged since BbS, so GHB could have benn sent to the RoS at the age he appears to be in the traielr.