If anything, i would say Xemnas is the nobody created when Terranort stabbed himself in the Final Episode. He and Ansem SoD have a striking resemblance to Terra. They even changed up Ansem SoD's model in KH3D a bit (his facial structure) where he is also comparable to Terra.
I think that's a really good point. In KH3D, when the Somebodies (for lack of a better word) reawaken in Radiant Garden's castle, Terranort is nowhere to be found. Ditto Braig and Isa. Ienzo later states: "when someone who has lost their heart is recompleted, they should return to the place where it happened." Given that Lea has "turned [the] castle upside-down" and not been able to find them, it stands to reason that Braig, Isa and Terranort were made into Nobodies at a different time to the rest of the apprentices and Lea. I think this is what Ienzo tries to explain to Lea a few times before being unceremoniously cut off.
In the opening, Terranort summons what looks to be MX's keyblade, and Braig questions whether he remembers now, or had never lost his memory. While it could be that Terranort was faking the loss of his memories, it's also plausible that he actually did lose them, and was visited by another incarnation of MX to fill him in on the plan. I think Australian Riku is on to something. It's entirely possible that Xemnas as a Nobody was in existence long before the rest of the apprentices became Nobodies, and arrived to inform Terranort of what he had to do. Maybe this awakened some part of Xehanort's memories, allowing Terranort to once again wield a Keyblade.
In response to the original post of the thread, I believe Nomura did once give a nice, vague comment that Xemnas had "possibly" chosen not to wield the keyblade. A requirment of being a keyblade wielder is possessing a strong heart, as Sephiroth0812 rightly says. So I think you're right; he intentionally chose not to wield it so as not to reveal that Nobodies were capable of having hearts, thus allowing him to manipulate the Organization and create the most docile vessels for Xehanort's heart. They would be more obedient or willing to become vessels without their own hearts and emotions.
Doesn't really make sense when you fight after the rest of the group is wiped out. Why keep it a secret at that point?
Fair point. But in DDD, YMX's copies wield the Ethereal Blades like Xemnas does in KHII (and his DDD boss fight with Sora). So it could be that it's a long-standing ability of Xehanort's and is just a weapon Xemnas has come to prefer using when releasing his opponent's heart isn't necessary.
Oh, and welcome to the forums, KingXehan0rt!
