Manuel I of Portugal
Manuel's mother was the granddaughter of King John I of Portugal, whereas his father was the second surviving son of King Edward of Portugal and the younger brother of King Afonso V of Portugal. In 1495, Manuel succeeded his first cousin, King John II of Portugal, who was also his brother-in-law, as husband to Manuel's sister, Eleanor of Viseu.
War of the Portuguese Succession
Instead, Ranuccio's mother's younger sister Catherine, Duchess of Braganza, claimed the throne, very ambitiously, but failed. Catherine, Duchess of Braganza was married to Duke John I of Braganza (descendant in male line from Afonso, 1st Duke of Braganza, an illegitimate son of John I of Portugal), who himself was grandson of the late Duke James of Braganza, also a legitimate heir of Portugal, being the son of infanta Isabella of Portugal, sister of Manuel I and daughter of infante Ferdinand, Duke of Viseu, second son of King Duarte I. The Duchess also had a son, Dom Teodósio of Braganza, who would be her royal heir and successor to the throne. The Duchess's claim was relatively strong, as it was reinforced by her husband's position as one of the legitimate heirs; thus they would both be entitled to hold the Kingship. Moreover, the Duchess was living in Portugal, not abroad, and was not underage, but 40 years old. Her weaknesses were her gender (Portugal had not had a generally recognized reigning queen) and her being the second daughter, there thus existed a genealogically senior claimant.
According to the old feudal custom, the line of succession of the Portuguese throne would have been:Both António and Philip were the grandchildren of King Manuel I of Portugal :On July 24, 1580, António proclaimed himself as King of Portugal and of the Algarves, in Santarém, which was followed by popular acclamation in several locations of the country. However, he governed in Continental Portugal for only 33 days, culminating in his defeat at the Battle of Alcântara by the Spanish armies led by Fernando Álvarez de Toledo, Duke of Alba on August 25. The Battle ended in a decisive victory for the Spanish Habsburgs, both on land and sea. Two days later, the Duke of Alba captured Lisbon.