PIERRE de Flandre (-1176 before Aug). The Genealogica Comitum Flandriæ Bertiniana names (in order) "Philippum, Matheum, Petrum et tres filias" as the children of "Theodericus filius ducis Alsatie [et] Sibillam", specifying in another manuscript that Pierre was "preposituram Brugensem et Audomarensem"[454]. Provost at Bruges and Saint-Omer. The Flandria Generosa specifies that "tertius frater Petrus…cum esset clericus et electus Cameracensis" but resigned the appointment and married "comitissam de Nevers"[455]. The Chronicle of Alberic de Trois-Fontaines also records that election of "Petrus frater comitis Flandrie Philippi et comitis Mathei Boloniensis" as Bishop of Cambrai and his resignation, followed by his marriage to "comitissam Nivernensem"[456]. He was elected Bishop of Cambrai in 1167, but resigned his ecclesiastical appointments in 1173 after the death of his older brother Matthieu[457]. Comte de Nevers 1175 in right of his wife. Robert of Torigny records the death in 1177 of "Petrus frater Philippi comitis Flandrensium", noting that he had been elected to the episcopate of Cambrai but left the spiritual life[458]. m (1176) as her third husband, MATHILDE de Bourgogne, widow firstly of EUDES [II] Seigneur d'Issoudun and secondly of GUY I Comte de Nevers, daughter of RAIMOND de Bourgogne Seigneur de Grignon et de Vitteaux [Capet] & his wife Agnès de Thiers Dame de Montpensier (1150-17 Dec [1219], bur Abbaye de Fontevrault). Robert of Torigny records the marriage in 1177 of "Petrus frater Philippi comitis Flandrensium" and "comitissa Nivernensis quæ fuerat uxor domini Isoldunensis castri"[459]. Her marriage to Pierre de Flandre is confirmed by the charter dated 1182 under which "Matildis comitissa" donated property to Cîteaux for the souls of "Guidonis comitis Nivernensis, Petri Flandrensis et Odonis" with the consent of "filie mee Agnes…filia comitis Guidonis et Sibilla filia comitis Petri flandrensis"[460]. She married fourthly ([1177/80], annulled on grounds of consanguinity 1181) as his first wife, Robert [II] de Dreux, who succeeded his father in 1184 as Comte de Dreux. After the annulment of her fourth marriage, Mathilde became a nun at Fontevrault. Pierre & his wife had one child