William de Braose, Third Lord of Bramber, was the eldest son of Philip de Braose, Second Lord of Bramber. William married Bertha de Pitres, daughter of Miles of Gloucester, Earl of Hereford. Through this marriage, William acquired lordship of Brecon and Abergavenny in 1166 because Bertha's brothers all died young without heirs. In 1174, William became sheriff of Hereford. He was succeeded as Lord of Bramber by his son, William.