William (II) de Braose had a son Philip which I believe has not been noted before.
I discovered this when examining a charter recently in Beatrice Lees’ book, Records of the Templars in England in the twelfth century. It is an agreement between the Templars and the monks of Sele Priory concerning the tithes of William de Braose. It is dated 1181 in the charter itself. The witness list contains Philip, the brother of William and also William’s son Philip.
However, 1181 is a problematic date since it is uncertain whether the William in question is William(II) or William (III). William(II) died just around this time.
Now William (II) had a brother Philip but no recorded son, while William (III) had a son Philip but no recorded brother. So the neat answer is that a son Philip for William (II) would also be a brother for William (III). So, without knowing which William is concerned in the charter, this is evidence for the existence of this son! ome that
Addition: It has been pointed out to me that this son of William (II) is also recorded in an 1140 confirmation charter in the "liber alba" of St. Florent Abbey, so has been known for some time.