It's not recreateable because it's too small. Land area isn't relevant here, what's relevant is that it's two provinces. Two provinces is just too small to be a de jure Kingdom, even if you existed historically. That's why Bulgaria (8 historic provinces) includes Wallachia and Moldovia to get it to 18, and Wales (6) was replaced with Brythonia (14 provinces in-game).
The ideas on this thread wouldn't help at all because at most they bring Navarra up to 9, which would reduce Castille to 5, and Aragon to 12. The minimum number of provinces in a kingdom is apparently 10, and the only land the King of Aragon actually owns in 1066 is in our expanded Navarra, so basically to improve Navarra we've abolished Castille and rendered Aragon unrecognizeable.
In other words once the devs made the design-decision to have de jure Kingdoms, and give them all meaningful sizes, it was guaranteed some poor powerful Iberian realm was gonna be left out. And once we have a 1066 start-date that left-out dude has to be the smallest, and least able to conquer Muslims: Navarra. It's surprising they found room for Portugal, Leon, Castille, Aragon and Al-Andulus.
The only kingdoms smaller then 10 on-map are Serbia and Bohemia. Bohemia could probably be expanded to include Silesia without breaking gameplay too much, but then it would be bigger then Poland (13 provs vs. 12). Serbia can't really be titular for reasons both political and practical (you need it to be there to simulate Balkan Balkanization properly). It could probably be expanded to include Wallachia, but that only gets it to 10, and if it's a big stretch to put Wallachia (aka: another way to spell Vlach-ia) into Bulgaria it's an even bigger stretch to put it in Serbia.
BTW, in early versions CK1 Navarra was createable and two provinces. this was fixed (before DV IIRC) largely because the devs decided it was too easy to become King of the tiny Kingdom.
Nick