John, Prince of Asturias and Girona, was the only son of King Ferdinand II of Aragon and Queen Isabella I of Castile, and heir apparent to both their thrones for nearly his entire life.
John, Prince of Asturias
Francisco Pradilla Ortiz's painting Retinue of the Baptism of Don Juan, son of the Catholic Monarchs, Along the Streets of Seville, 1910
Tomb of Prince John at Real Monasterio de Santo Tomás in Ávila
Ferdinand II was King of Aragon from 1479 until his death in 1516. As the husband of Queen Isabella I of Castile, he was also King of Castile from 1475 to 1504. He reigned jointly with Isabella over a dynastically unified Spain; together they are known as the Catholic Monarchs. Ferdinand is considered the de facto first king of Spain, and was described as such during his reign, even though, legally, Castile and Aragon remained two separate kingdoms until they were formally united by the Nueva Planta decrees issued between 1707 and 1716.
Portrait by Michael Sittow
Ferdinand the Catholic swearing the fueros as the Lord of Biscay at Guernica in 1476
Columbus soliciting aid of Ferdinand's wife Isabella.
Wedding portrait of Ferdinand and Isabella