Edmund Beaufort, 4th Duke of Somerset

He was the son of Edmund Beaufort, 2nd Duke of Somerset, and became duke at the death of his brother Henry in 1464. (The dukedom was somewhat theoretical, depending on how one views the legitimacy of the forfeiture of the title by the 3rd duke during the reign of Edward IV, which was retracted by Henry VII long after Somerset's death.)

Edmund commanded the Lancastrian forces at the Battle of Tewkesbury, and was captured and executed after the battle. His death ended the legitimate Beaufort line and, with the death shortly thereafter of Henry VI, left his cousin Margaret Beaufort and her son, the future Henry VII, as the leading representatives of the House of Lancaster.