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.
History of Portugal
Philip II of Spain, through his mother Isabella of Portugal, also a grandson of Manuel I, claimed the Portuguese throne and did not recognize António as king of Portugal. The king appointed Fernando Alvarez de Toledo, 3rd Duke of Alba, as captain general of his army. The duke was 73 years old and ill at the time, but Fernando mustered his forces, estimated at 20,000 men, in Badajoz, and in June 1580 crossed the Spanish-Portuguese border and moved towards Lisbon.