Simon, known as 'the Bald', was the son of Amaury III de Montfort, comte d'Evreux, sire de Montfort, and his second wife Agnès de Garlande. He was count of Evreux from 1140 and lord of Montfort l'Amauri from 1137 to his death. With his wife Mahaut he had three children, Simon IV, Amaury V and Bertred, who would all have progeny.
Vassals of the king of France for Montfort and of the king of England for Evreux, the Montforts were caught in the rivalry between the two kings. Amaury III had attempted to resolve the problem by leaving Evreux to his elder son Amaury IV and Montfort to his younger son Simon III, but the death of Amaury IV three years later reunited the two areas under Simon.
Simon chose in favour of the English king and gave up to him the strongholds of Montfort, Rochefort and Epernon. As a result the young Louis VII, king of France, 'could not come and go freely from Paris to Orléans or Etampes because of the Normans established by King Henry in the castles of the counts of Evreux'.
Later Simon reconciled with the young Louis VII, who gave him custody of the castle of Saint-Léger-en-Yvelines.
Simon died in March 1181.
Amauri de Montfort, brother and heir [of Simon] (a). In 1098 he aided William II against his brother's castles of Montfort and Epernon. After the death of William de Breteuil in 1103, Amauri supported the claim of William's Burgundian nephew, Renaud de Grancei, to succeed to his estates against that of his Breton nephew, William de Gael. On the death sp. in 1118 of his maternal uncle, William, Count of Evreux, Amauri claimed the comte, and when Henry I denied him the inheritance led a widespread revolt, and obtained possession of Evreux. In the following year Henry besieged Evreux, but his nephew Theobald, Count of Champagne, reconciled him and Amauri, who surrendered the castle to the King and thereupon received his uncle's comte.
In 1123 Amauri joined the revolt of Waleran, Count of Meulan--subsequently husband of his daughter Agnes--against Henry. Next year Amauri fought at Bourghteroulde, and was captured when fleeing from the field by William de Grandcourt, who, rather than hand over his prisoner to captivity, went into exile with him, but before the end of the year Amauri made his peace with the King, and seems to have maintained friendly relations with him during the rest of the reign.
He m. 1stly, Richeude, daughter of Baldwin, Count of Hainault, from whom he separated. He m. 2ndly Agnes, niece of Stephen de Garlande, with whom he received Rochefort and Gournay-sur-Marne; her parentage is uncertain. She was probably the mother of his eldest son, Amauri, and certainly of his second son Simon, and of a daughter, Agnes (e). He d. 18 or 19 Apr, year unkown, and was buried at the Abbey of Haute-Bruyere, which he had founded. [Complete Peerage VII:Appendix D:713-4].
Gui, called 'le Rouge', was a seneschal of France of the house of Monthléry. He was a younger son of Gui I de Monthléry, seigneur de Monthléry et Chevreuse, and Hodierne de Gometz-la-Ferté.
From his parents he inherited the castles of Rochefort-en-Yvelines, Gometz and Châteaufort, while the family seat Monthléry went to his older brother Milon I. Gui is considered to be the builder of the castle of Bréthencourt.
Gui had three children with his first wife Elisabeth, of whom a daughter, possibly called Béatrice or Agnès, would have progeny, becoming the second wife of Anceau de Garlande, comte de Rochefort.
His second wife was Adélaide de Crécy, dame de Gournay-sur-Marne, widow of Bouchard II, comte de Corbeil, who brought the castles of Crécy-en-Brie and Gournay-sur-Marne to the marriage. Of their children Hugues and Lucienne, the latter would have progeny.
Abbot Suger of Saint-Denis wrote that Gui was a close friend of Philippe I, king of France, who appointed him as his seneschal. Suger wrote that he also received the title of count. Gui had a dominant influence at the royal court, to the considerable benefit of his family, in the centre of a closely related group of families of castle lords on the Ile de France. He took part in the Crusade of 1101 in the Lombard contingent, in part to restore the family honour after his nephew Gui Troussel had deserted at the siege of Antioch during the First Crusade.
After his return Gui immediately resumed the leading position at court. He looked to cement the position of his family through a marriage into the royal family. In 1104 he married a grand-niece Elisabeth de Monthléry to Philippe de France, the king's son from his second marriage, and in the same year he married his daughter Lucienne de Rochefort to Louis, the heir to the throne, the future King Louis VI 'the Fat'. Shortly afterwards he passed the position of seneschal to his son Hugues. However in 1107 the dauphin Louis determined to free himself from the influence of the house of Monthléry-Rochefort and he divorced Lucienne. He withdrew the position of seneschal from Hugues and awarded it to Anceau de Garlande, Gui's son-in-law.
The family of Monthléry then launched a long insurgency by the castle lords of the Ile de France that preoccupied King Louis VI for years. In 1108 Gui and his son Hugues had to defend the castle of Gournay against the king's army. Gui succeeded in winning the powerful Thibaut IV-II, comte de Blois et Chartres, to his cause, but Thibaut was defeated by the king in attempting to relieve the siege. Gui had to give up the castle of Gournay, and he died shortly after. His son Hugues then led the insurgency, which continued until 1118.