The core of Sora’s situation is succinctly described when he decides to leave Destiny Islands again to kick off the plot of KH3D, saying, “I am who I am because of them.” Sora takes in a little piece of everyone he meets and grows because of that—he is influenced by so many other people and would not be the Sora we know if none of those people existed. Then we have Xehanort, who from the very first game has always been focused on finding new people to possess, finding others who he can turn into new Xehanorts. His reasons for this and how these plans have expanded can only be related through recent spoilers, so I’m going to skip over that for now and try to condense the point.
Sora allows himself to be changed by others. Xehanort changes others into him.
And I feel like this could be an allegory telling us that we shouldn’t force our own views on other people, coercing them into being more like us. Instead, we should take in what others have to offer, let them influence us, and grow as a person because of that interaction. I’ve seen people interpret Aqua’s storyline from Birth by Sleep as having a similar message to this, so it might not be coincidental that she ends up being doing better against Xehanort than Ven and Terra: both arcs might be saying that only someone who understands the benefits of having an open, receptive heart can stop someone with an open heart that aggressively seeks its way into others.
We’ll have to wait to see where Aqua’s character goes, but Sora has already accepted his connectedness and embraces it without hesitation. The scene I’m thinking of is near the end of KH3D so I don’t want to give too much away, but of the two Xehanorts who hear his declaration, one is baffled and a little frustrated, and the other seems unaffected and silently activates Final Boss Mode. The idea that these connections can be beneficial is completely lost on Xehanort, and I’m going to go ahead and predict that that is why he can never win. (You know, in the end. He’s definitely doing pretty well now.) Maybe it’s cliché and cheesy and whatever, but if a villain cannot comprehend a hero’s power, then there’s a pretty good chance that power is going to be their undoing; said power being some variant of “the power of friendship” certainly doesn’t hurt either. But, that’s a whole thing in and of itself.
My point is that I never fully grasped how Sora and Xehanort were being set up as opposites, and that the often-noted similarity does have a little more depth than is immediately apparent. And I thought that was kind of cool.
(Though I guess this doesn’t really account for those characters who were spawned from Sora? I mean he still encourages them to be their own person, but I don’t know?)