Radulf I de Tosny and Hugo, Archbishop of Rouen in 942, were brothers but it is not known which was older. The birth date of about 912 for Hugh is based on the assumption that Hugh would have reached the canonical age of 30 at the time of his appointment by William I of Normandy "Longsword" as archbishop of Rouen.
991 Radulf son of Hugo was named by Pope John XV in a description of the reconciliation arranged by the Pope's envoy between Æthelred II and Richard I following a dispute over Norman support for raids in England by Vikings: "nobis relatum est a compluribus de inimicitia Æthelredi Saxonum Occidentalium regis necnon et Ricardi marchionis" in an act dated at Rouen 1 May 991 "ex parte Ricardi Rogerus episcopus, Rodulfus Hugonis filius." [1]
[1] Peter Stewart, Origin and early generations of the Tosny family (Self-published, 2013), 8, [OriginTosnyFamily].