The Genealogica Comitum Flandriæ Bertiniana names (in order) "Balduinum et Guillelmum" as sons of "Rodbertus [et] Clementiam". His parentage is recorded by Orderic Vitalis, who says that he was "still a boy" when he succeeded his father in 1111 as BAUDOUIN VII Count of Flanders. He refused to return her marriage portion to his mother, who instigated a rebellion of south Flemish barons with the help of Baudouin III Comte de Hainaut, but was forced to submit. The Continuatio Valcellensis of Sigebert's Chronica records in 1115 that “Balduinus comes Flandriæ” captured “castrum Encres” from “Hugone Camdavena”, who had usurped it, and granted it to “Karolo consobrino suo”. The Continuatio Valcellensis of Sigebert's Chronica records in 1117 that “Balduinus comes Flandriæ” besieged “castrum sancti Pauli” held by “Hugo Camdavena”, who had devastated territory, but had returned it after the mediation of “Eustathio comite Boloniæ”.
William of Malmesbury and Orderic Vitalis record that Count Baudouin supported Guillaume "Clito" de Normandie against Henry I King of England in 1118, invaded Normandy as far as Arques, but in Sep 1118 was wounded "for his helmet being battered with repeated strokes, he received an injury to his brain". He passed the last ten months of his life in the monastery of St Bertin. He designated Charles of Denmark as his successor on his deathbed, although the accuracy of this statement is dubious if his brain injuries were severe. The Annales Blandinienses record that "Balduinus comes, Rodberti iunioris et Clementiæ filius" was 26 years old when he became a monk after a distinguished military career. The Vita Karoli Comitis Flandriæ records the death "1119 XV Kal Iulii" of Count Baudouin, and his burial at St Bertin. 1