William was very fortunate in his marriage to Berta. All of her brothers died young without heirs so she brought a number of important lordships to the de Braoses in 1166. These included Brecon and Abergavenny.

William became Sheriff of Hereford in 1174. His interest in Sussex was maintained as he confirmed the grants of his father and grandfather for the maintenance of Sele Priory and extended St. Mary's, Shoreham.