ANSEAU [I] de l’Isle, son of ADAM [III] de l’Isle & his wife --- (-18 Mar before 1162). Sire de l'Isle. He founded the abbey of Notre-Dame-du-Val before 1127. "Ansellus de Insula" granted duty exemptions to Saint-Leu d’Esserent, with the consent of "uxoris illius Mabillæ filiorumque suorum Adæ atque Theobaldi", by charter dated 1149[398]. The necrology of the Priory of Saint-Martin-des-Champs records the death "XV Kal Apr" of "Ansellus dominus de Insula"[399].
m MABILIE, daughter of ---. "Ansellus de Insula" granted duty exemptions to Saint-Leu d’Esserent, with the consent of "uxoris illius Mabillæ filiorumque suorum Adæ atque Theobaldi", by charter dated 1149[400]. According to Père Anselme, she was Mabilie “fille de Lancelin de Beauvais et d’Alix de Bulles”, but he cites no primary source[401]. The names Lancelin and Manassès, introduced into the Isle-Adam family after this marriage, do suggest a connection with the Bulles family. However, no mention has been found of the involvement of the Isle-Adam family in the complicated question of the inheritance of the seigneurie de Bulles during the 12th century.
Anseau [I] & his wife had six children