Listen to the Summary of Sarah Gristwood's Game of Queens in 20 minutes. Please note: This is a summary & not the original book. Isabella of Castile was the first queen regnant of Castile, and she was married to Ferdinand of Aragon, who was king of Aragon and Castile. They had a daughter, but no son. Isabella's position changed when her half-brother Enrique died without a child to follow him, and she took the throne with Ferdinand by her side...