- --From Wikipedia--
Katherine Swynford (also spelled Synford), nÃƒÂ©e (de) Roet (also spelled (de) Rouet or (de) Roelt (25 November 1350 Ã¢â‚¬â€œ 10 May 1403), was the daughter of Payne (or Paen) de Roet, a Flemish herald from Hainault who was knighted just before his death in battle. His children included Katherine, her older sister Philippa, a son, Walter, and the eldest sister, Isabel de Roet, (who died Canoness of the convent of St. Waudru's, Mons, c. 1366). Katherine became the third wife of the English prince John of Gaunt Duke of Lancaster, and their descendants were the Beaufort family, which played a major role in the Wars of the Roses. Henry VII, who became King of England in 1485, derived his claim to the throne from his mother Lady Margaret Beaufort, who was a great-granddaughter of Katherine Swynford.
Katherine was educated at the convent of Romsey in Hampshire. About 1366, at the age of 16, Katherine married Hugh Swynford (1340-1372), an English knight from the manor of Kettlethorpe in Lincolnshire, and bore him at least two children; Thomas (Sept 21, 1368-1432), Blanche (born May 1, 1367), and likely the Margaret Swynford (born c. 1369) who was nominated a nun at the prestigious Barking Abbey by the command of Richard II in 1377). Katherine then became attached to the household of John of Gaunt, Duke of Lancaster, as governess to his two daughters , Philippa of Lancaster and Elizabeth Plantagenet, (the sisters of the future Henry IV of England) by his first wife Blanche. Sometime before 1373, she became his official mistress. Katherine's sister Philippa, a member of the household of Queen Philippa of Hainault, wife of Edward III, married the poet Geoffrey Chaucer, whose poem The Book of the Duchess commemorated Blanche's death in 1369.
Two years following the death of his second wife Constance of Castile, John and Katherine married on 13 January 1396 in Lincoln Cathedral, three years before he died. The four children Katherine had borne John of Gaunt had been given the surname "Beaufort" and were already adults when they were legitimized by this marriage with approval by King Richard and the Pope. The Beauforts were later barred from inheriting the throne by a clause inserted into the legitimation act by their half-brother, Henry IV.
Katherine survived John by only four years, dying on 10 May 1403. She was then dowager Duchess of Lancaster. Her tomb, and that of her daughter Joan Beaufort, are under a carved-stone canopy in the sanctuary of Lincoln Cathedral. Joan's is the smaller of the two tombs; both were decorated with brass plates Ã¢â‚¬â€ full-length representations of them on the tops, and small shields bearing coats of arms around the sides Ã¢â‚¬â€ but those were damaged or destroyed in 1644 during the English Civil War.