Guillaume of Jumièges records that one of the daughters of “Rodulphum” and his wife “Erembergam...natam in quadam villa Calcini territorii...Cavilla” married “Osberno de Crepon de qua natus est Willelmus filius Osberni”. Orderic Vitalis calls Guillaume nepos of Hugues Bishop of Bayeux. "Willelmus et frater eius Osbernus" donated "terram…Herchembaldus vicecomes et Turoldus, comitissæ Gunnoris camerarius" and revenue from land received by "Croco et Erchembaldus filii eiusdem Erchembaldi vicecomitis" to the abbey of Sainte-Trinité at Rouen, with the consent of "matre eorum Emma", for the soul of "patris sui Osberni cognomento Pacifici", by charter dated to [1035/60], signed by "…Godeboldi, Daneboldi, Ansfredi filii Osberni, Gisleberti filii Turgisii…". "Willelmo filio Osberni et…Ælicia eius uxore filia Rogeri de Thoneio" founded the abbey of Lyre by charter dated 1046. "…Guillelmi filii Osberni…" witnessed the charter dated 1054 under which Guillaume II Duke of Normandy confirmed the donation of "terram…Sancta Columba…dedit Niellus clericus" to the abbey of Mont-Saint-Michel. "…Willelmi filii Osberti, Rotgerii de Monte Golmerii, Richardis vicecomitis Abrinchensis…" witnessed the charter dated [1055/56] under which Guillaume II Duke of Normandy "in pago…Constantino, villam…Flotomannum" to Saint-Florent de Saumur.
He founded the monastery of Corneilles in  "on his own estates". "…Guillelmus filius Osberti…Guillelmus filius Guillelmi filiii Osberti…" witnessed the charter dated to  under which Guillaume II Duke of Normandy granted "Brenerias" to the abbey of Bayeux. "Ansfredus, Osberni de Ou vicecomitis, postea…Hierosolimitani monachi, filius…cum conjuge mea Emma" offered "unicum filium meum…Goiffredum" as a monk at Sainte-Trinité de Rouen, with the consent of "dominis meis Emma, Osberni dapiferi uxore et filiis eius Willelmo et Osberno…Willelmo…principe Normannorum", by undated charter. "Willelmus filius Osberti…" witnessed the charter dated 29 Aug 1060 under which "milite…Richardo…fratribus Willelmo…atque Balduino" donated "Gausberti Villa" to Chartres Saint-Père. Orderic Vitalis names “...Willermus Osberni filius, ducis cognatus et dapifer...” among the leading lords under Guillaume II Duke of Normandy.
The Brevis Relatio de Origine Willelmi Conquestoris records that "Willelmo dapifero filio Osberni" contributed 60 ships towards the invasion of England in 1066. Orderic Vitalis names “...Guillermus Osberni filius...” among those who took part in the battle of Hastings. The Chronique de Normandie, based on le Roman de Rou, records that William I King of England made "le Conte Rogier de Montgomery et Guillaume le filz Osber" his two "Marechaulx d’Engleterre" after the conquest of England. "Erchenbaldo filio Erchenbaldi vicecomitis", on the point of leaving "ultra mare", donated property to Sainte-Trinité de Rouen, with the consent of "rege Anglorum et duce Normannorum Guillelmo", by undated charter, signed by "…Willelmi filii Osberni, Emmæ matris eius, Ansfredi filii Athlæ…". He fought at the battle of Hastings.
Earl of Hereford: Florence of Worcester records that King William left "fratrumque suum Odonem Baiocensem episcopum et Willelmum filium Osberni quem in Herefordensi provincia comitum" when he went to Normandy 21 Feb . "Willelmus comes filius Osberni dapiferi" donated rights in "totius silvæ Longum Bothel" to Sainte-Trinité de Rouen by charter dated 1068, which states that later "Willelmus…filius eius" confirmed the donation. Orderic Vitalis records that “Rodbertus Ricardi filius Eboracensis præsidii custos” was killed, that “Marius Suenus, Gaius Patricius, Edgarus Adelinus, Archillus et quatuor filii Karoli” attacked “munitionem regis in Eboraco”, that “Willelmus cognomento Maletus, præses castrensis regi” announced to the king that he would be forced to withdraw unless reinforcements were sent, and that the king constructed a second castle in York which entrusted to “Guillelmum comitem Osberni filium”, dated to 1069. Florence of Worcester records that "Willelmi Herefordensis comitis" seized treasure from monasteries in England 17 Feb . Orderic Vitalis records that King William granted “insulam Vectam et comitatum Herfordensem” to “Willelmo dapifero Normanniæ Osberni filio”, and sent him “cum Gualterio de Laceio” to fight “contra Britones” [Welsh], during which they first invaded “Brachaniaunos” and defeated “Guallorum reges Risen et Caducan ac Mariadoth”, dated to 1071.
Orderic Vitalis records that King William sent "Guillelmum Osberni filium" to Normandy to govern "cum Mathilde regina...provinciam" in “anno quinto regni sui” [1070/71] and that he was sent by Philippe I King of France to help Arnoul Count of Flanders against his uncle Robert “le Frison” but was killed in battle “X Kal Mar”, his body being returned to Normandy for burial “in cœnobio Cormeliensi”. The Chronicon Lyrensi records that "Willelmus filius Osberni" was killed by "Roberto Frison die Dominica Septuagesimæ" in 1072 and buried "Apud Cormelias". Robert of Torigny's De Immutatione Ordinis Monachorum records that "Willermus filius Osberni Normanniæ dapifer et cognatus Willermi ducis" was buried "apud Cormelias". The necrology of the monastery of Ouche records the death "20 Feb" of "Willelmus Britolii comes". The necrology of Lyre monastery records the death "20 Feb" of "Guillelmus comes institutor hujus loci". Guillaume of Jumièges records that “Willelmus...filius Osberni, propinquus ducis Willelmi” founded “duo monasteriain honorem...Mariæ unum apud Liram...alterum apud Cormelias”, adding that he was buried at Cormeilles. 1