Margaret Beaufort, Countess of Devon English noble (1409–1449) Parents Margaret Beaufort, Countess of Somerset John Beaufort, 1st Earl of Somerset Children Joan Courtenay Agnes Courtenay Henry Courtenay John Courtenay, 15th Earl of Devon Thomas Courtenay, 14th Earl of Devon Elizabeth Courtenay Siblings Edmund Beaufort, 2nd Duke of Somerset Thomas Beaufort, Count of Perche Joan Beaufort John Beaufort, 1st Duke of Somerset Henry Beaufort, 2nd Earl of Somerset Partners Thomas de Courtenay, 13th Earl of Devon