Ancestral Roots, line 222-28, gives William's wife as Bertha de Braiose, dau of William and Bertha of Hereford, who according to Line 177-5 did not marry until 1150-and would have their dau. Emma born no earlier than 1166. In my line, Bertha married Walter, William's grandchild.
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John Ravilious, in a post to soc.genealogy.medieval, agreed that Bertha married the grandson of William de Beauchamp, d. 1170. He also agrees that William married a Maud de Braose, instead of Bertha, but he places Maud as daughter of William & Agnes, who I have as grandparents. I think they were too old to be Maud's parents. He also, in a later post, thinks she may have been a 2nd wife, with the unknown first wife being mother of William. I did not see the reasoning behind this.