Alternately, Ferdinand and Isabella don't marry.
I presume then Isabella would marry Alfonso V of Portugal. Any other possible husbands?
How far afield do you want to look?
Juana, la Beltraneja succeded as the Queen of Castile, while Isabel married Ferdinand and became queen consort of Aragon.
Alternatively, have Alfonso, Prince of Asturias (and son of John II of Castile) not die of a sickness/the plague/some random crap. I'm sure Castillian succession laws are agnatic-cognatic, and thus, would pass to the next male heir.
I actually made a thread on that, but then someone said it wouldn't change much and that unification would happen some time anyway.
Well, according to the TV series Isabel, Alfonso died of sickness, which is related to plague I think.Alternatively, have Alfonso, Prince of Asturias (and son of John II of Castile) not die of a sickness/the plague/some random crap.
Alternatively, have Alfonso, Prince of Asturias (and son of John II of Castile) not die of a sickness/the plague/some random crap. I'm sure Castillian succession laws are agnatic-cognatic, and thus, would pass to the next male heir, which meant he'd be king over either Henry's daughter Joanna or Henry and Alfonso's half-sister Isabella.
A united Navarre and Aragon might not be unfortunate. It would be a buffer between Castille and France and tie Euskadera (the Basque regions together with Catalonia. If "Navarragon" was able to get San Sebastian, Bilbao, both or both and Santander as Atlantic seaports, the combined state could be a viable colonial power, at least in the 16th-18th Centuries and possibly beyond. And Euskadera is rich in iron and coal for industrialization.If Charles, prince of Viana, survives to succeed his father, Isabella can still marry Ferdinand without uniting Castile and Aragon. This has the unfortunate side effect that it results in uniting Navarre and Aragon.
The ruler of Navarragon also has a claim to the French throne...A united Navarre and Aragon might not be unfortunate. It would be a buffer between Castille and France and tie Euskadera (the Basque regions together with Catalonia. If "Navarragon" was able to get San Sebastian, Bilbao, both or both and Santander as Atlantic seaports, the combined state could be a viable colonial power, at least in the 16th-18th Centuries and possibly beyond. And Euskadera is rich in iron and coal for industrialization.