Spanish Royalty. King of Aragón, Majorca, Sicily and Valencia; Count of Barcelona; King of Naples. Son of Ferdinand I of Aragón and Eleanor of Alburquerque, he was of the House of Trastámara. He was born in Medina del Campo, Castile, and had a hereditary right to the kingdom of Sicily and was in possession of much of Corsica. In 1421 the childless Joan II of Naples adopted him and he became heir to the throne of Naples. He hired the mercenary Braccio da Montone to defeat Louis III of Anjou, another claimant to the throne. Louis' forces were led by Muzio Attendolo Sforza who was supported by Pope Martin V. Alfonso therefore swore allegiance to the antipope Benedict XIII. In May 1423 Alfonso had Joan's lover, the powerful Gianni Caracciolo, arrested and attempted to arrest Joan as well. She turned to Sforza for assistance and repudiated her adoption of Alfonso, naming Louis III as her heir. Alfonso had to return to Spain where his brothers were at war with Castile. Joan died in February 1435, leaving her kingdom to René of Anjou, brother of Louis III. Alfonso tried to intervene but in the Battle of Ponza during the siege of Gaeta he was taken prisoner. He so charmed his captor that he was able to go free and resume his battle for Naples. René arrived in Naples in 1438 but was unsuccessful against Alfonzo. Finally on 26 February 1443 Alfonso was triumphant and became King of Naples. To commemorate his victory he had an arch added to the main gate of Castel Nuovo. Alfonso also founded the Academy of Naples and was a patron of the arts. He died in Castel dell'Ovo, Naples of pleurisy in 1458 while planning the conquest of Genoa. His brother Juan II of Aragón inherited his Spanish possessions as well as Sicily and Sardinia. He had married Maria of Castile (1401–1458) in Valencia on 12 June 1415 but they had no issue. His natural son Ferdinand I of Naples (1423 – 1494) succeeded him as king of Naples.