Amauri III, 6th seigneur de Montfort was said, by both Oderic and Robert de Torigny, to be the son of Simon I by Agnes, sister of William, Count of Evreux.2 He was a witness where Simon I, seigneur de Montfort attested, with his son Amauri, another charter of Philip confirming the gift to St. Magloire by "quidam miles de castro qui Montefortis vocatur Symon nomine" of the churches of St. Peter and St. Laurence situate "in eodem castro" as "S. Simonis de castro Montefortis ... S. Almarici Simonis filii" in 1072.1 Amauri III, 6th seigneur de Montfort was born circa 1080 at Montfort, Yvelines, Île-de-France, France. He was the son of Simon I, seigneur de Montfort and Agnes d' Évereux.1 Amauri III, 6th seigneur de Montfort was the successor of Simon II "le Jeune", 5th seigneur de Montfort; 5th Seigneur of Montfort.3 Amauri III, 6th seigneur de Montfort assisted William II against his brother Simon's castles of Montfort and Epernon in 1098.2 He was a witness where Simon II "le Jeune", 5th seigneur de Montfort defended his castles of Montfort and Epernon successfully against William II, and his own brother Amauri, but was himself taken prisoner in this war, in 1098.3 Amauri III, 6th seigneur de Montfort supported the claim of William de Bréteuil's Burgundian nephew, Renaud de Grancei, to succeed to his estates against that of his Breton nephew's, William de Gael, in 1103.2 6th Seigneur of Montfort at France.2 He married Richeude de Hainaut, daughter of Baudouin II "de Jerusalem", comte de Hainaut and Gräfin von Hennegau Ida von Löwen, in 1110?; His 1st.2 Amauri III, 6th seigneur de Montfort and Richeude de Hainaut were divorced; Separated for possible consanquinity?2 Amauri III, 6th seigneur de Montfort married Agnes de Garlande, daughter of Anseau de Garlande, senechal de France and Agnès de Rochefort Montlhéry, before 1120; His 2nd.2 Amauri III, 6th seigneur de Montfort died 18 or 19 April at year unknown.4 He was the predecessor of Amauri, 7th seigneur de Montfort; 7th Seigneur of Montfort.4