William de Braose, fourth baron married Maud de S. Valerie, "a prudent and chaste woman," by whom he had three sons. He incurred the enmity of the Welsh when, in revenge for the death in 1175 of his uncle, Henry of Hereford, he invited to the castle of Abergavenny Seisyll ap Dyfnwal and others of the Welsh of his lordship and treacherously put them to death. Giraldus exonerates him from blame and refers to the religious zeal shown by William and his wife. He was a benefactor of the priories of Brecon and Abergavenny . [1]
[1] Welsh Biography Online, [URL].