Cokayne's "Complete Peerage" (Leicester, p.532, note h), identifies the 5 sons of HUGH, the Domesday tenant and suggests that though unproven, Robert is, by far, the most likely of the 5 brothers to have been the grandfather of PETRONILLA DE GRANDMESNIL. Petronilla was the heiress of the Norman Grandmesnil estates and Robert was the son who inherited these estates from his father. (Todd Farmerie, however, tempers this fact with the observation that Robert ended up being deprived of his lands, which could then have been regranted to one of his line or any of the others' familiies.) It now appears that Hugh's brother, William is the most likely candidate for Petronilla's grandfather.
Robert married 1) AGNES of BAYEUX, 2) Emma d'Estouteville, 3) Lucy FitzCana. The identity of any children that each wife may have borne is not known. Oderic says that Robert had a dau, Agnes, who m. Robert de Moulins, but otherwise, he gives no information as to his children.