<P> For analysis of politics, diplomacy and social history, see Tudor period . </P> <P> The Tudors descended on Henry VII's mother's side from John Beaufort, 1st Earl of Somerset, one of the illegitimate children of the 14th century English prince John of Gaunt (the third surviving son of Edward III) by Gaunt's long - term mistress Katherine Swynford . The descendants of an illegitimate child of English royalty would normally have no claim on the throne, but the situation became complicated when Gaunt and Swynford eventually married in 1396, when John Beaufort was 25 . The church retroactively declared the Beauforts legitimate by way of a papal bull the same year, confirmed by an Act of Parliament in 1397 . A subsequent proclamation by John of Gaunt's legitimate son, Henry IV, also recognised the Beauforts' legitimacy but declared them ineligible ever to inherit the throne . Nevertheless, the Beauforts remained closely allied with Gaunt's legitimate descendants from his first marriage, the House of Lancaster . </P> <P> On 1 November 1455, John Beaufort's granddaughter, Margaret Beaufort, Countess of Richmond and Derby, married Henry VI's maternal half - brother Edmund Tudor, 1st Earl of Richmond . It was his father, Owen Tudor (Welsh: Owain ap Maredudd ap Tudur ap Goronwy ap Tudur ap Goronwy ap Ednyfed Fychan), who abandoned the Welsh patronymic naming practice and adopted a fixed surname . When he did, he did not choose, as was generally the custom, his father's name, Maredudd, but chose that of his grandfather, Tudur ap Goronwy, instead . This name is sometimes given as Tewdwr, the Welsh form of Theodore, but Modern Welsh Tudur, Old Welsh Tutir is originally not a variant but a different and completely unrelated name, etymologically identical with Gaulish Toutorix, from Proto - Celtic * toutā "people, tribe" and * rīxs "king" (compare Modern Welsh tud "territory" and rhi "king" respectively), corresponding to Germanic Theodoric . </P> <P> Owen Tudor was one of the bodyguards for the queen dowager Catherine of Valois, whose husband, Henry V, had died in 1422 . Evidence suggests that the two were secretly married in 1429 . The two sons born of the marriage, Edmund and Jasper, were among the most loyal supporters of the House of Lancaster in its struggle against the House of York . Henry VI ennobled his half - brothers: Edmund became Earl of Richmond on 15 December 1449 and was married to Lady Margaret Beaufort, the great - granddaughter of John of Gaunt, the progenitor of the house of Lancaster; Jasper became the first Earl of Pembroke on 23 November 1452 . Edmund died on 3 November 1456 . On 28 January 1457, his widow Margaret, who had just attained her fourteenth birthday, gave birth to a son, Henry Tudor, at her brother - in - law's Pembroke Castle . </P>

Where did the name house of tudor come from