According to the wiki for both Queen Isabella and Pedro Girón Acuña Pacheco, the pair were supposed to wed, but Pedro died on his way to get married to Isabella. What if he hadn't died and the two had been wed?
https://en.m.wikipedia.org/wiki/Pedro_Girón_Acuña_Pacheco
https://en.m.wikipedia.org/wiki/Pedro_Girón_Acuña_Pacheco