- --From Wikipedia--
John of Gaunt, 1st Duke of Lancaster (6 March 1340 Ã¢â‚¬â€œ 3 February 1399) was a member of the House of Plantagenet, the third surviving son of King Edward III of England and Philippa of Hainault. He gained his name "John of Gaunt" because he was born in Ghent (in today's Belgium), then called Gaunt in English. John exercised great influence over the English throne during the minority reign of his nephew, Richard II, and during the ensuing periods of political strife, but did not openly associate with opponents of the King.
John of Gaunt's legitimate male heirs, the Lancasters, included Kings Henry IV, Henry V, and Henry VI.
John's legitimate descendants also included his daughters Philippa of Lancaster, Queen consort of John I of Portugal and mother of King Edward of Portugal, known as "Duarte" in Portuguese, and of the famous Henry the Navigator. John was also the father of Elizabeth, Duchess of Exeter, the mother of John Holland, 2nd Duke of Exeter through his first wife, Blanche; and by his second wife, Constance, John was the father of Katherine of Lancaster, Queen consort of Henry III of Castile, granddaughter of Peter of Castile and mother of John II of Castile.
John of Gaunt fathered five children outside marriage, one early in life by one of his mother's ladies-in-waiting, and four, surnamed "Beaufort," (for the castle in which they were born) by Katherine Swynford, Gaunt's long-term mistress and third wife. The four Beaufort children, three sons and a daughter, were legitimized by royal and papal decrees after John married Katherine in 1396. Descendants of the marriage to Katherine Swynford included their son Henry Beaufort, Bishop of Winchester and eventually Cardinal; their granddaughter Cecily Neville, mother to Kings Edward IV and Richard III; and their great-grandson Henry Tudor, who became King of England after the Battle of Bosworth Field in 1485 and established the House of Tudor.
When John of Gaunt died in 1399, his estates were declared forfeit to the crown, as King Richard II had exiled John's son and heir, Henry Bolingbroke, in 1398. Bolingbroke and Richard II were first cousins; their fathers were brothers. Bolingbroke returned from exile to reclaim his confiscated inheritance and deposed the unpopular Richard. Bolingbroke then reigned as King Henry IV of England (1399Ã¢â‚¬â€œ1413), the first of the descendants of John of Gaunt to hold the throne of England.
John of Gaunt was buried alongside his first wife, Blanche of Lancaster, in the nave of Old St. Paul's Cathedral in an alabaster tomb designed by Henry Yevele (similar to that of his son in Canterbury Cathedral).