Ferdinand was the son of John II of Aragon by his second wife, the Aragonese noblewoman Juana Enriquez. He married Infanta Isabella, the sister by a different mother of Henry IV of Castile, on 19 October 1469 in Ocaña. He became Ferdinand V of Castile when Isabella succeeded her brother as Queen of Castile in 1474. The two young monarchs had to begin with a civil war against Juana, princess of Castile (also known as Juana la Beltraneja), who claimed to be the daughter of Henry IV. They won. Ferdinand succeeded his father as King of Aragon in 1479. This meant the Crown of Castile and the various territories of the Crown of Aragon were united in a personal union. For the first time since the 8th century this created a single political unit which might be called Spain, although the various territories were not properly administered as a single unit until the 18th century.