Guillaume of Jumièges names “Herleva Fulberti cubicularii ducis filia” as the mother of “Willelmus...ex concubina Roberti ducis...natus“, and that after Duke Robert died “Herluinus...miles” married her by whom he had “duos filios Odonem et Robertum”. Florence of Worcester names Robert as the brother of King William I "but only on his mother's side". Orderic Vitalis records that Guillaume Duke of Normandy granted “multis honoribus in Normannia et Anglia” to “Herluinus...de Contavilla...filios eius: Radulfus, quem de alia conjuge procreaverat, fratresque suos uterinos: Odonis et Rodbertum”.
[Vicomte. Geoffrey Richard Driscoll Tobin has suggested that the third and fourth witnesses in the following charter were Robert and Eudes, sons of Vicomte Herluin. "Comes Eudo et nepos eius Gaufridus, Robertus vicecomes et frater eius Eudo…Guichomarus filius Alani vicecomitis…" witnessed a charter dated to 1050 relating to the abbey of Saint-Georges de Rennes. No brothers named Vicomte Robert and Eudes have been identified among the Breton nobility at the time, and the suggestion is plausible. If correct, it has several implications. Firstly, the order of their names indicates that Robert was older than his brother Eudes. Secondly, this would be the only primary source which indicates that Robert bore the vicecomital title (before the death of his father). Thirdly, the dating of the charter is probably correct considering the suggested date of Eudes’s appointment as bishop.]
Orderic Vitalis records that he was installed as Comte de Mortain in 1063 by his half-brother Guillaume II Duke of Normandy, after he dispossessed Guillaume Werlenc. Guillaume of Jumièges records that “Willelmus cognomento Werlencus de stirpe Richardi magni comes...Moritolii” plotted rebellion against Guillaume II Duke of Normandy, as reported to the duke by “tyro de familia sua...Robertus Bigot”, and that the duke expelled him to Apulia and granted his county to “Robertum fratrem suum”. Orderic Vitalis names “...Rodbertus comes Moritoliensis, Willermi ducis uterinus frater...” among the leading lords under Guillaume II Duke of Normandy. King William I granted him nearly all the land of Cornwall as a reward for his participation at the battle of Hastings in 1066, but he does not seem to have been created Earl of Cornwall, continuing to be referred to as "comes Moritoniensis". "Robertus Moretonii comes frater Villelmi Anglorum regis et Normannorum principis" granted property to the abbey of Saint-Benoît-sur-Loire by charter dated 9 Jan 1083. He joined his brother Eudes in the 1088 rebellion against King William II but was pardoned.
The necrology of the church of Mortain records the death "8 Dec" of "Robertus comes Moretonii fundator istius ecclesie" 2
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EARLDOM of CORNWALL
Robert, Count of Mortain in Normandy, one of the two sons of Herluin de Conteville, by Herleve, mother of William the Conqueror, was b. about 1031. About 1050 he received, from his uterine brother, William, then Duke of Normandy, the comte of Mortain, and was thenceforth known as Count of Mortain. He accompanied William in the invasion of England, where he was in command of the chivalry of the Cotentin at the battle of Hastings, 1066. His share of the spoil was one of the greatest, as, with the exception of the lands of the King and the Church, he received nearly the whole of the county of Cornwall, and is, consequently, usually considered Earl of Cornwall, though only known as Comes Moritoniensis. At the time of Domesday, he was possessed of 797 manors in various counties, besides the borough of Pevensey in Sussex, etc. In 1069 he, with Robert, Count of Eu, defeated the Danes in the parts of Lindsey, with great slaughter. He joined his brother, the Earl of Kent in 1088 in a rebellion against William II in favour of his brother Robert Courthose, but was subsequently pardoned. He m. 1stly, before 1066, Maud, daughter of Robert de Montgomery, Earl of Shrewsbury, by his 1st wife, Mabel, daughter and heir of William Talvas (5th son of William de Belleme, Seigneur of Alencon and Belleme). She was buried in the Abbey of Grestain. He m. 2ndly, Almodis. He d. 8 Dec 1090, and was buried with his 1st wife. 3
Also referred to as Robert de Burgo and Robert de Conteville.