MATHIEU [I] de Beaumont, son of IVES [II] Comte de Beaumont & his second wife Adelais --- ([1070/73]-1 Jan 1155). According to Père Anselme, Mathieu [I] Comte de Beaumont was the son of Ives [II] Comte de Beaumont and his second wife Adela[59]. Douet d’Arcq repeats the information, citing no other source[60]. No primary source has been identified which confirms that the affiliation is correct. However, the mention of Comte Mathieu [I] for the first time in [1090/91] suggests that it might be, assuming that he and his full siblings were born much later than their older half-sister. His birth date is estimated based on this mention, but also bearing in mind the date of his death which suggests that it is unlikely that he was born much before [1070]. Comte de Beaumont. Orderic Vitalis records that "Matthæus comes de Bellomonte et Guillelmus de Guarenna" fought against Robert de Montgommery “de Bellême” who had attacked neighbouring lands, dated to [1090/91][61]. “...Matthæicomitis de Bello-monte...” subscribed the charter dated 1096 under which Etienne Comte d’Aumâle donated property to Beauvais Saint-Lucien[62]. Suger's Vita Ludovici names "strenuum et nobilem comitem Matthæum Bellimontensem" among those captured by William II King of England, dated to [1097][63]. “Matheus comes et uxor mea Beatrilidis cum filiis meis Ivone et Matheo” granted freedoms to the men of Bernes at the request of the canons of Saint-Germain-l’Auxerrois de Paris, by charter dated 1110[64]. Suger's Vita Ludovici records the campaign by "Bellimontensis comes Matthæus" and "Drogonem Monciacensem" against "Hugonem Claromontensem", stating that Matthieu married the latter's daughter[65]. Orderic Vitalis records that "Burchardus de Monte Morencii, aliique prudentes" advised Louis VI King of France not to invade Normandy, dated to 1119, that "Mathæus comes de Bellomonte et Guido de Claromonte...ac Burchardus de Monte Morentii" led the invasion and fought at Brémule[66]. "Mattheus comes, filius eius Matheus..." subscribed the charter dated 1136 which records an agreement between the priory of Saint-Leu d’Esserent and the inhabitants of the town regarding duties on wine[67]. "Mattheus comes Belli montis" exempted Saint-Leu d’Esserent from duties, with the consent of "Matheo comite patre meo et Hugone fratre meo et Mathilde comitissa uxore mea", by charter dated 1154[68]. This charter shows that Mathieu [I] resigned the countship in favour of his son before his death, presumably due to his old age. The necrology of the Priory of Saint-Martin-des-Champs records the death "IV Non Jan" of "Mathei comitis Bellomontis"[69]. The necrology of the abbey of Notre-Dame du Val records the death "Kal Jan" of "Matheus comes Bellimontis"[70].
m (before 1101) BEATRIX de Clermont, daughter of HUGUES de Clermont-en-Beauvaisis & his wife Marguerite de Roucy (-after 1110). Suger's Vita Ludovici records that "Bellimontensis comes Matthæus" married the daughter of "Hugonem Claromontensem"[71]. The Genealogiæ Scriptoris Fusniacensis refers to a sister of "comes Rainaldus" as wife of "Matheus comes de Bello-monte, de qua genuit alterum Matheum comitem et fratrem eius et filias"[72]. The Chronicle of Alberic de Trois-Fontaines refers to, but does not name, one of the sisters of "comitem Rainaldum" as "comites Bellimonti"[73]. “Matheus comes et uxor mea Beatrilidis cum filiis meis Ivone et Matheo” granted freedoms to the men of Bernes at the request of the canons of Saint-Germain-l’Auxerrois de Paris, by charter dated 1110[74]. Dame de ½ Luzarches.
Mathieu [I] & his wife had [four or more] children