Cyril Sebastian, I love your posts and truly admire your knowledge and research. Thank you.
Just one thing: Cataluña/ Catalonia has never been a kingdom; it was a principality under the crown of Aragón.
From Wiki: )King Ferdinand died on 2 April 1416, and) Alfonso succeeded him as king of Aragon, Valencia, and Majorca and count
of Barcelona ( yes, the same title Juan Carlos' father chose to hold).
Alfonso the Magnanimous[a] (1396 – 27 June 1458) was the King of Aragon and King of Sicily (as Alfonso V) and the ruler of the Crown of Aragon from 1416 and King of Naples (as Alfonso I) from 1442 until his death.