GUILLAUME [I] de Dampierre, son of GUY [I] Seigneur de Dampierre & his wife Helvide de Baudémont (-before 1161). "Guido de Dampetra…et uxor eius…Elvidis et filii Anserici et Guillelmus" approved the donation by "Lethericus de Baudimonto" to the Templars at Provins, by charter dated 1133[594]. The Chronicle of Alberic de Trois-Fontaines names (in order) "Anserici, Guilelmi, Andree et Milonis" as brother of "Guido de Dampetra" Bishop of Chalon[595]. Seigneur de Dampierre, de Saint-Dizier et de Moeslain. 1133/60. "Simon dominus Belfortis" donated property to Chapelle-aux-Planches by charter dated 1152 in which he names "Hugone fratre meo domino de Brecis", in the presence of "domini Wilermi domini de Dampetra […et Heleidis mater eius…] et Milonis de Planceii"[596].
m as her first husband, ERMENGARDE [Basilie] de Mouchy, daughter of DREUX [IV] de Mouchy & his wife Adélaïde ---. The primary source which confirms her parentage and two marriaes has not yet been identified. 1174. She married as her second husband ([1161]) Dreux de Mello Maréchal de France. 1197.
Guillaume [I] & his wife had five children