GUILLAUME [I] de Saint-Omer, son of --- (-before 1128). Châtelain de Saint-Omer. Châtelain Guillaume witnessed the charter dated to [1097/1100] under which Clémence Ctss of Flanders granted land to "son neveu Anselme de Parenti"[726]. "…Willelmus castellanus Sancti Audomari, Rogerus castellanus Islensis, Geraufus castellanus Casletensis…Robertus nepos Rogeri castellani Islensis…" signed the charter dated 15 Feb 1113 under which Baudouin VII Count of Flanders attested that "Walterio Hisdinensi" had committed to defend the abbey of Saint-Silvin d´Auchy[727]. "…Willelmus castellanus Sancti Audomari, Hugo nepos eius, Gillebertus frater eius…" signed a charter dated 29 Nov 1121 under which Charles Count of Flanders donated property to the monastery of Bourbourg[728]. "…Willelmus castellanus de Sancto Audomaro, Hugo nepos eius, Giselbertus frater eius…" witnessed the charter dated 7 Jul 1123 under which "Hugo de Sancto Paulo cognomen habens Campdaveine" donated property to the monastery of Bourbourg, in the presence of Charles Count of Flanders[729]. [m firstly ---. No direct information has been found about this supposed first marriage. However, Guillaume [I]´s supposed grandsons were already recorded, and therefore were probably adult, in the early 1140s (see below). If this is correct, Hosto´s paternal grandmother would have probably been too old for a second marriage in [1128], when Guillaume [I]´s wife Aganitrude is recorded with her second husband. This suggests that Guillaume [I]´s children were born from an earlier unrecorded first marriage.] m [secondly] as her first husband, AGANITRUDE, daughter of ---. Her family background and two marriages are confirmed by the Vita Karoli Comitis Flandriæ which records that, after Charles Count of Flanders was killed, Bertulf took refuge with "Alardi Warnesunensis" who had married "neptem illius Aganitrudem", adding that she was "castri…sancti Audomari quondam castellanam"[730]. This source does not specify the name of her first husband, but as the châtelain de Saint-Omer is named Guillaume in the sources dated between 1113 and 1126, it is likely that this was the Aganitrude´s husband. She married secondly Alard de Warneton. Guillaume [I] & his [first] wife had one child