John II of Castile was King of Castile and León from 1406 to 1454. He succeeded his older sister, Maria of Castile, Queen of Aragon, as Prince of Asturias in 1405.

Maria of Castile was Queen of Aragon and Naples as the spouse of Alfonso V of Aragon. Maria acted as the regent of Aragon during the reign of her spouse, as he was absent during most of his reign; her regencies lasted between 1420 and 1423 and between 1432 and 1458. She was also briefly Princess of Asturias in her own right as the heiress presumptive to the throne of Castile. She succeeded her father, Henry III of Castile, as Princess of Asturias in 1402.