He was captured and imprisoned (as an act of retaliation) by Llywelyn the Great, ruler of most of Wales, in 1229, but was given relative freedom because he was related to the prince by marriage in several ways — his daughter, Isabella, was married to Llywelyn's only legitimate son. However, in the following year, Llywelyn is said to have discovered that his wife, Joan, had committed adultery with William, and had William hanged on May 2, 1230. Joan herself was later pardoned.
Lord of Briouze in Normandy and of Bramber in Sussex, he was son and heir of Philip deBraose, of the same, by Aenor, daughter and heir of Juhel, son of Alvred, Lord of Barnstaple and Totnes.
Younger son of Sir John deBraose, Lord of Bramber and Gower, and Margaret, daughter of Llewelyn, Prince of North Wales, Richard deBraose was summoned 12 December 1276 to 14 Jun 1287, and to attend the King at Shrewsbury 28 June 1283.
Williamde Cantelou, on 25 July 1238, obtained her wardship and marriage together with the custody of Abergavenny and other lands left to her, and shortly thereafter, she was married to his son, William.