4. Ferdinand and Isabella
Isabella of Castile and Ferdinand of Aragon were second cousins who requested a papal dispensation in order to marry in 1469. Pope Paul II refused to grant one, wary of the unification and resultant increased power of the two kingdoms. Who created the falsified papal bull to allow them to marry remains unknown, but a false document appeared, and the two were married. Each of them were heir apparent to the thrones of their respective kingdoms. Ferdinand became King of Aragon in 1479 following the death of his father, King Juan II. In September of that year, threats to Isabella’s right to the throne of Castile were resolved through treaty with Portugal. Their marriage was the beginning of a modern unified Spain.
Together they served as the Catholic Monarchs, a title bestowed by Pope Alexander VI in 1494. By then the two monarchs had presided over the wars driving the Moors from Spain, expanded the territories under their rule, and sponsored the expedition to the New World undertaken by Christopher Columbus. They also initiated the expulsion of Jews from Spain, in a process known to history as the Spanish Inquisition. Isabella died in 1504, and when her daughter Joanna appeared an inept ruler, Ferdinand ruled Castille as a regent while retaining the throne of Aragon. Ferdinand died in 1516. Joanna’s son, Charles I of Spain, eventually established the Habsburg Dynasty there, and the beginnings of the Spanish Empire in both the Old World and the New.