In the Flodoard Annales his listed as the son of Manasse ["Gislebertus, filius Manasse, a rege Rodulfo descivit propter Avalonem castrum quod ab eo Emma regina abstulerat"]. On 31 October 920, a charter of Hervé, bishop of Autun ["Heriveus ejusdem miseratione humilis Eduorum episcopus"], mentioned his mother Ermengarde (Hirmingardis) and his brothers ["dilectæ genetricis nostræ domnæ Hirmingardis venerabilis comitissæ et fratrum nostrorum"], his avunculus bishop Walo ["domnus Walo, pius presul et noster avunculus"], and was signed by Ermengarde and her sons Walo, Giselbert, and Manassès ["Hirmingardis Dei misericordia comitissa firmavit. Signum Walonis filii ejus. Signum Gisleberti filii ejus alterius. Signum Manassæ filii ejus."]. In June 924, count Giselbert consented to a donation of his mother Ermengarde, in a charter of Saint-Marcel-lès-Chalon ["... munificentiam Ermengardis comitisse et deo devote, seu filii ejus Gisleberti comitis illustris, ... S. Ermengardis que fieri et firmare rogavit. S. Gisleberti qui consensit."]