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.
João I, Duke of Braganza
After the disaster of the Battle of Ksar El Kebir, where heirless King Sebastian of Portugal died, the aged Cardinal Henry of Portugal had become King. Because Henry was old and was not allowed to have legitimate children, a dynastical crisis occurred even before the death of the Cardinal. The Duke of Braganza supported his wife's claim to the throne (she was a granddaughter of King Manuel I). Philip II of Spain (another grandson of Manuel I and also claimant to the throne), tried to bribe him to abandon his wife's pretensions, offering him the Vice-Kingdom of Brazil, the post of Grand-Master of the Order of Christ, a license to send a personal ship to India every year, and the marriage of his eldest son Teodósio of Braganza to one of his daughters (either Isabella Clara Eugenia or Catherine Michelle). The Duke of Braganza, influenced by his wife, refused the proposal.