Bizarro

Yeah, I'm aware of that and I agree. I was just saying that he's a new incarnation in the sense that he's not a Heartless or a Nobody. I definitely don't think he's half a person, nor is MX, but that's what atheist seems to be suggesting here.

See, I was more under the impression that the Master Xehanort in 3D is the "ultimate recombined Xehanort" Yen Sid mentioned back in Re:Coded's ending. Remember that when someone's Heartless and Nobody is destroyed, they reform. All the other incarnations were just taken from different times if I understood the subs correctly. We never actually see Apprentice Xehanort in the game aside from flashbacks, so I'm thinking MX still has control over the reformed Terra's body; only this time, Terra's body has completely taken the form of MX (sort of like Riku and Ansem SoD from KH1). In a sense, I guess you COULD say AX is the mastermind if he's still using Terra's body, but since he regained his memories and regained the old man's form I'd still say he's just MX again.

They were born from Apprentice Xehanort, but Apprentice Xehanort is just Master Xehanort in another vessel. Like I said, MX is the true form of everything - Terranort was more or less just a plot device for Ansem SoD.

The interview is legit, yeah, but I believe he said the true FORM (as in singular) of Ansem and Xemnas would be revealed at the end, which - of course - is Master Xehanort. Terranort isn't really as relevant as people often make him out to be, and would technically just be Ansem SoD anyway; MX is the source and "true form" of everything.

Fact of the matter is, the game officially and specifically calls him "Young Xehanort" and also places the old Master Xehanort of higher authority and greater standing, so I'm hardly inclined to believe YMX and MX are just two halves of a whole being. This seems to be an entirely new Xehanort incarnation associated only with time manipulation as opposed to Heartless and Nobodies. And atheist, why do you keep advocating this idea that Xemnas in 3D is Xemnas' Nobody? That's completely stupid and makes absolutely no sense. That also goes for your Ansem SoD theory, as he was clearly a part of the Organization and not just Riku's memories/inner darkness haunting him like in CoM.

Are we getting subtitles for the final Young Xehanort and Riku confrontation by any chance? I'd think that might shed a lot of light on YMX's time-travelling circumstances. While I did see the translations posted in the comments on youtube of it, it's sort of badly translated and I can't really understand it.

Pretty much this. This is wrong. The first to accomplish time-travelling was Ansem SoD, and only when he'd discarded his body (he'd presumably lost that ability when acquiring Riku's body) - however, YMX's circumstances are still fairly unknown at the moment and there's been nothing to suggest he discarded his body at all. Also, Master Xehanort is NOT a Nobody; there's nothing to imply he was ever an empty vessel at any point.