John was born at Medina del Campo (in the Crown of Castile), the son of King Ferdinand I of Aragon[2] and Eleanor of Alburquerque.

[5] There followed the long Navarrese Civil War, with alternations of success and defeat, ending only with the death of the prince of Viana, possibly by poison administered by his father in 1461.

[6] The institutions of the Principality of Catalonia, who had adopted the cause of Charles and who had grievances of their own, called in a succession of foreign pretenders in the ten years' Catalan Civil War.

He was forced to pawn Roussillon, his Catalan possession on the north-east of the Pyrenees, to King Louis XI of France, who refused to part with it.

[5] In his old age John was blinded by cataracts, but recovered his eyesight with an operation (couching) conducted by his physician Abiathar Crescas, a Jew.