At some time after 1421 Margaret married
Thomas Courtenay, 13th Earl of Devon (1414–1458), for whom she bore three sons and five daughters. Her sons were all killed or executed during the
Wars of the Roses due to their strong adherence to the
Lancastrian cause, and left no children, and thus the senior line of the Courtenays was extinguished. Margaret's children included the following: •
Thomas Courtenay, 14th Earl of Devon (1432 – 3 April 1461), eldest son and heir, who shortly after 9 September 1456 married Mary of Anjou, illegitimate daughter of
Charles, Count of Maine. The marriage was without children. As a Lancastrian supporter during the
Wars of the Roses, he was taken prisoner at the
Battle of Towton, in which the victor was the
Yorkist Edward IV, then attainted and beheaded at
York. All his honours, including the original
Earldom of Devon, became forfeited. whilst other authorities treat his earldom as a new creation. Following the temporary reversal in the dominance of the Yorkists and the temporary restoration of the Lancastrian king
Henry VI, Stafford was beheaded in August 1469 and John Courtenay was restored to the honours of his family, with the attainder of 1461 having been reversed and thereby became 15th/16th Earl of Devon. However, the position was short-lived as the Yorkists definitively terminated the reign of Henry VI in April 1471 at the
Battle of Barnet and on 4 May 1471 Courtenay was slain during the
Battle of Tewkesbury, having commanded the rear of the Lancastrian army. On his death the earldom fell into
abeyance between his sisters or their descendants. • Joan Courtenay, (born c. 1447), who married, firstly, Sir Roger Clifford, second son of
Thomas Clifford, 8th Baron de Clifford, beheaded after
Bosworth in 1485. She married, secondly, Sir William Knyvet of
Buckenham, Norfolk. • Elizabeth Courtenay (born c. 1449), who married, before March 1490, Sir Hugh Conway. • Anne Courtenay • Eleanor Courtenay • Maud Courtenay • Agnes Courtenay. Two of Margaret's nieces were also named Margaret Beaufort.
Margaret Beaufort, Countess of Stafford, was the mother of
Henry Stafford, 2nd Duke of Buckingham, and
Margaret Beaufort, Countess of Richmond and Derby, was the mother of King
Henry VII. ==Ancestry==