Original: When Ferdinand succeeded his father as King of Aragon in 1479 , the Crown of Castile and the various territories of the Crown of Aragon were united in a personal union creating for the first time since the 8th century a single political unit referred to as España ( Spain ) , the root of which is the ancient name Hispania .
Simplified: Ferdinand and Isabella had 5 children , Isabella of Asturias , Juan of Aragon , Joanna of Castile , Maria of Aragon , and Catherine of Aragon .