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
The Duke of Alba met little resistance and in July set up his forces at Cascais, west of Lisbon. By mid-August, the Duke was only 10 kilometers from the city. West of the small brook Alcântara, the Spanish encountered a Portuguese force on the eastern side of it, commanded by António, Prior of Crato (a grandson of King Manuel I of Portugal who had proclaimed himself king), and his lieutenant Francisco de Portugal, 3rd Count of Vimioso. In late August, the Duke of Alba defeated António's force, a ragtag army assembled in a hurry and composed mainly of local peasants, and freed slaves at the Battle of Alcântara. This battle ended in a decisive victory for the Spanish army, both on land and sea. Two days later, the Duke of Alba captured Lisbon, and on 25 March 1581, Philip II of Spain was crowned King of Portugal in Tomar as Philip I. This cleared the way for Philip to create an Iberian Union spanning all of Iberia under the Spanish crown.