Family
William married first in 1406 Elizabeth (died 1420), the daughter of Sir John Bluet of Raglan manor and widow of Sir James Berkeley. Elizabeth, "the lady of Raggeland", inherited Raglan Castle with her husband James Berkeley, who later died in 1405 or 1406. Before marrying Berkeley she had married and become the widow of Sir Bartholomew Picot. Elizabeth's third marriage, to William, was childless.
William married secondly heiress Gwladys ferch Dafydd Gam (died 1454), described by Welsh poet Lewys Glyn Cothi as 'The Star of Abergavenny' for her beauty. She was the daughter of Sir Dafydd Gam and the widow of Sir Roger Vaughan of Bredwardine. All three men had been part of the Welsh contingent that fought with King Henry V of England in France, including the Battle of Agincourt.
William and Gwladys had children:
William Herbert, 1st Earl of Pembroke (1423–1469) took the surname Herbert. William's allegiance to Richard, Duke of York, and Richard Neville, 16th Earl of Warwick, branded him Edward IV's Welsh "master-lock". He was the first full-blooded Welshman to enter the English peerage and he was knighted in 1452. He married Anne Devereux, daughter of Sir Walter Devereux, in 1449, and they had issue. The modern Herbert family that holds the earldoms of Pembroke, Montgomery, and Carnarvon, are descended from an illegitimate son of this William Herbert.
Sir Richard Herbert of Coldbrook, near Abergavenny; died at the Battle of Edgcote in 1469.
Elizabeth married Sir Henry Stradling (1423–1476), son of Sir Edward Stradling (d. c.1394) and Gwenllian Berkerolles, sister and co-heir of his neighbour, Sir Lawrence Berkerolles. Reversing alliances from the previous generation, Henry and his brothers-in-law were hostile to the Henry VI reign. Henry went on a pilgrimage to the Holy Land in 1476. Henry died on 31 August 1476 on his journey back to England and was buried at Famagusta, Cyprus. Thomas, Elizabeth and Henry's young son, died on 8 September 1480.
Margaret married Sir Henry Wogan, steward and treasurer of the Earldom of Pembroke, tasked with securing war material for the defence of Pembroke Castle. Henry and his father, John Wogan of Picton, witnessed an act of Bishop Benedict in 1418. Their son, Sir John Wogan, was killed at the Battle of Edgcote in 1465, fighting by the side of his uncle, William Herbert, Earl of Pembroke.
Other children less consistently attributed to Gwladys and William include: Maud, Olivia, Elizabeth (who married Welsh country gentlemen, John ab Gwilym), and Thomas Herbert.
The Cornish family of Thomas (Thomas of Lelant, Thomas of Crowan, Thomas of Tremayne, Thoms, and the Bosarvanes of St Just), all patrilineally descended from "Richard Thomas gent. of Wales" are acknowledged as legitimate agnatic descendants of William ap Thomas in the 1620 Visitation of Cornwall.
The Visitation records state "This coate of Pr pale nebule Ar. B. was ye coate armor of Sr Willm ap Thomas, from whom this familye chalengeth to be descended."
Descendants of this family include Members of Parliament, such as John Thomas who sat in the 1555 Parliament for the Cornish borough of Mitchell, members of the clergy such as Methodist minister the Reverend William Courtenay Thomas and his descendants, and related pioneering families in Australia.