Also, they are too apart from Xehanort and Terra, a bit of Aprentice Xehanort while not recovering his memory (that is why he started himself calling Ansem, and Ansem SoD is even in KH 3 about his researching while he was AX)
Xemnas has more of Terra because is the body, and about the armor you said in a ultimania interview it is stated that the armor in KH2 and BBSFM (No Name) is Xehanort's one in the past, the original, and in KH3 is a recent one
When I said I felt Xemnas had "more of Terra" I was specifically comparing his actions to that of Nortless, who should be the other "half" of their split from Apprentice Xehanort (which I only even brought up because you said that the two of them felt "not Xehanort"). I only wanted to highlight that yes, they are not actually fully Xehanort because you've got a little Terra in there, too. I'm aware it's his body. While it's great that you wanted to explain their origins, I suppose, I'm not really sure why you felt the need to do so. That should all be common knowledge at this point. Unless you were just agreeing with me? I don't know. I apologize if I am simply not understanding you, but I am having a little bit of trouble following your English.
They all can do it, even with part of MX's heart, as we see three of the five summoning, same or not, YX, TX and MX (During KH 3)
Again, I'm not sure if you are just trying to agree with me? Nothing I said has ever contradicted that they
can summon a Keyblade. I've stated such multiple times. All I have been trying to do is postulate reasons why they would choose not to, or why it would be a poor logical decision to do it long term. There is never an absolute answer given, so all we can do is just hypothesize based on what we see, the reasons they would choose not to.
Also, the reason why they would have the ability is likely BECAUSE of MX's influence (and some part Terra), not in spite of it, so I don't really understand your caveat above.
Maybe you didn't quite understand me when I mentioned using "their own hearts" to wield?
It seems, at least consistently so far in the series that 1 Heart = 1 Keyblade. Yes, there are some shenanigans now with the duel wielding introduced in 3 but lets just ignore that for right now because until that wrench was thrown in the system the rules had been stated several times and were fairly clear.
As stated by Nomura previously: "Sora can wield two Keyblades at once because he has Ventus's [heart] as well as his own."
So, Ven has 1 Keyblade, Sora has 1 Keyblade, Xehanort would have 1, Terra would have 1, etc. This was what was causing issues in Days for Roxas and Xion because, at the time, the two of them were both trying to use Sora's Keyblade. They were literally fighting over the 1 Keyblade available to them, because they were all connected to Sora's heart. Roxas then is able to use 2 later because Xion is eliminated from the picture, and he taps into both Sora's Keyblade and Ven's Keyblade.
The only reason why you get people with multiple Keyblades is if they have other peoples' hearts inside of them that they can then "utilize" for their own means.
However, Roxas gets his own heart down the line, separate from Sora or Ven. So when Roxas returns, it is clear that he at this point has his "own" heart (same with Xion) so the two of them, when they use Keyblades, are using their OWN and not, say, borrowing Sora's or Ven's any more.
The reason why this 1 heart = 1 keyblade thing
matters for this discussion is because MX was literally splitting his heart around, so everyone who has a piece of that pie should be able to use his ability to wield. That isn't really in question. BUT that doesn't change the fact that there is just 1 Keyblade to go around. The only way for them to all be wielding their own,
separate Keyblades without worry is if they each, separately, grew their own heart
independent to Xehanort just like Roxas did. Which, like I said before, is incredibly problematic towards their long-term goal of, you know,
being Xehanort.
Them summoning a Keyblade, or the same Keyblade, or even a different one, in quick succession in a scene or two does not discount any of this. Have you played Days? There are literally missions with both Xion and Roxas fighting at the same time. Yes it is weird and kind of breaks physics as we know it but...again, Keyblades are really wonky magical things.
The issue would only really arise, in theory, if all the Norts collectively decided that they were going to keep using their Keyblades at the same time. When Roxas and Xion did that for an extended period they were making each other sick. Again, I don't know if such a thing would happen to the Norts, but who knows. It might.
If it makes it easier, lets say instead of Keyblades it was the keys to the "family car". The Nort family all only has one dilapidated rusty
candy van car to share between them all. Master Xehanort, the head of the family, has made a unilateral decision that, since Terranort is the best driver among them, he gets main control over the car keys. Could Xemnas borrow the keys on Monday to go to the store and pick up some extra hair gel? Well certainly he could! He has a drivers license! But oops, the car isn't in the driveway because it's being driven right now by Terranort who is cruising around taunting teenagers (
"Today is the day you all LOSE") then speeding off cackling. Xemnas doesn't want to risk not getting his hair gel on time, so instead of sitting around waiting for the car to come back he just
warps hops on a skateboard like a super cool dude.
So then there we are, sitting on the clocktower eating ice cream when we see Xemnas go flying by on his skateboard, hair windswept, in desperate need of some gelling. And we wonder to ourselves,
"What the hell was in my tea" "Why isn't he driving? He has a car and a license...?" The answer is that generally, it is easier to just keep the peace and find a different method of transportation than having to argue over the one shared car in the family and risk not getting his errands done at all. It might seem silly, because a car is genuinely a faster mode of transportation, but if Xemnas never knows 100% for sure if that car is going to be sitting there in the driveway waiting for him, he might as well be better off accepting he is going to need to rent a chocobo or walk instead and will just adjust his plans to accommodate that first.
I'm not saying this is definitively, 100% the explanation, but it's the one that makes the most sense to me and none of the lore or scenes we have seen so far really discount it as far as I'm aware.
It really could honestly be as simple as "they don't want to."
It is interesting to think about what is going on in Xemnas' and Nortless' heads that they would chose to handicap themselves with using a less superior weapon. I suppose at least with Nortless he made his own Keyblade as fast as he could using Riku's body and princess hearts. Maybe Xemnas was just trying his best to keep up appearances. If everyone knew he could use his own Keyblade then he would have to actually do work collecting hearts (or at least pretend to) in order to maintain faith among the other org members instead of
beckoning to the moon/kicking his feet back on an oversized throne by himself/mumbling at his imaginary armor friend doing what he does best. Like was mentioned earlier, it's likely he didn't really want/need the original organization to succeed in the whole heart gathering thing as it was just an excuse to gather people so why put in your best effort?