English family comprising the descendants of Edward III's son John of Gaunt, Duke of Lancaster, by his liaison with Catherine Swynford; the name derived from a lordship that Gaunt had held in France, the modern Montmorency-Beaufort near Bar-sur-Aube. The four offspring of the union were legitimized after their parents' subsequent marriage (1396) but were, by their half brother, Henry IV, expressly excluded from succession to the crown. The first generation comprised John (d. 1410) created Marquess of Somerset and Marquess of Dorset; Henry, cardinal bishop of Winchester; Thomas (d. 1426); and a sister, Joan. In the next generation, the possible claim to the throne of John's third (but then first surviving) son, Edmund Beaufort, 1st Duke of Somerset (d. 1455), precipitated the Wars of the Roses, in which the remaining male members of the house were killed. Margaret Beaufort, Edmund's niece, became the mother of the future king Henry VII.