Could someone rule England and Castile by the 14th century, if so how long could it last along with other changes from it?
Would any dynasty be able to keep the two for very long?
My impulse is to say "no", but the Romans did manage to govern the two and much more besides, so who knows.
I have a feeling feudalism would stop it from surviving for very long and France being in between.
Do it the other way round, with deaths amongst the English royal family (druing the War of the Roses?) making it possible for a Castilian monarch to claim England successfully on the basis of their own descent from John of Gaunt?What about having John of Gaunt successfully claimed Castile? That would give Castile an English King with a claim on England. The only question is how to get the Lancastrians the English throne.
Do it the other way round, with deaths amongst the English royal family (druing the War of the Roses?) making it possible for a Castilian monarch to claim England successfully on the basis of their own descent from John of Gaunt?