William Devereux (1219 to 1265)

William Devereux (1219 to 1265), was an important Marcher Lord, and held Lyonshall Castle controlling a strategically vital approach to the border of Wales. The castle’s significance was heightened by the rebellion of Llywelyn ap Gruffudd, Prince of Wales. With strong family ties to the politically powerful families of Cantilupe and Giffard, his support was strongly sought after by Henry III and Simon de Montfort throughout the Second Barons' War.

William Devereux was born in 1219, the son of Stephen Devereux and Isabel de Cantilupe. She was the daughter of William de Cantilupe (died 1239) and Mazilia Braci. His father had risen to be a powerful member of the inner circle of William Marshal, 1st Earl of Pembroke, which led to a prominent role during the regency of Henry III. The Devereux family had been prominent along the Welsh Marches since the conquest, and William was a descendent of the Domesday land holder, William Devereux. The coat of arms for Devereux portrayed on his mother's grant in 1242 was 'a fess and in chief three torteauxes.' His coat of arms was described as "argent, fess and three roundels in chief gules" or "gules od un fesse d'argent ove turteaus d'argent en le chief."

At his father’s death, William was only 8 years old, and came under the sway of his maternal relatives including William de Cantelupe (died 1254), Lord of Abergavenny; Walter de Cantilupe, Bishop of Worcester; and Thomas de Cantilupe, Bishop of Hereford. His interests on the Welsh Marches were further guarded by his paternal uncles: John Devereux of Bodenham and Decies and Nicholas Devereux of Chanston. The close relationship of the Cantelupe family with Simon de Montfort, 6th Earl of Leicester would later influence Devereux’s decisions during the Second Barons' War.