BAUDOUIN de Hainaut, son of BAUDOUIN IV "le Bâtisseur" Comte de Hainaut & his wife Alice de Namur (1150-Mons 17 Dec 1195). The Chronicon Hanoniense names "Balduinum primum, Godefridum secundum, Balduinum tercium, Heinricum quartam" as the sons of "Alidis comitissa Hanonensis …cum viro Balduino comite"[302]. The Genealogica comitum Buloniensium names "Balduinum" as son of "Hainoensi comiti Balduino" and his wife Alice, specifying that he married "Margaretam filiam Theoderici Flandrensis comitis" and had children (unnamed)[303]. The Chronicle of Alberic de Trois-Fontaines names (in order) "comitem Balduinum, Henricum de Seburgo et quatuor sorores" as children of "comiti Balduini de Haynaco"[304]. "Comite Hanoniensis nepote suo [=[Heinricum] comes Namurencis] ex sorore" is referred to, but not named, in a contemporary report on the fire at the abbey of Gembloux[305]. He succeeded his father in 1171 as BAUDOUIN V Comte de Hainaut, and as heir to Henri Comte de Namur et de Luxembourg. He supported Philippe II King of France when war broke out with Philippe Count of Flanders in 1183 over the inheritance of the counties of Vermandois and Valois[306]. After the unexpected birth in 1186 of Ermesinde, daughter of Henri Comte de Namur et de Luxembourg, the latter revoked his assurance concerning Baudouin's succession in these two counties. In 1188, Comte Henri was obliged to reinstate Baudouin as his heir after a verdict in the latter's favour from Heinrich VI King of Germany. Comte Baudouin attacked Namur, captured Comte Henri and obtained a confirmation of his position from Emperor Friedrich I who also secretly created him Marquis de Namur. Under a compromise reached in 1190, Baudouin received Namur immediately, and the expectation of Laroche and Durbuy after the death of Henri; the fate of Luxembourg was not mentioned. The creation of the Marquisate of Namur, and the elevation of Baudouin as Marquis de Namur, was announced at Worms in 1190[307]. "Ludovici advocate Hasbanie" sold the advocacy of Flône, and other rights relating to churches of Liège, to "domino comiti Hainoensi…Balduino", by charter dated 1190, witnessed by "Wilhelmus frater comitis Hainoensis, Alardus de Cimai, Nicholaus de Barbentione…"[308]. Although designated as successor in Flanders by his brother-in-law Philippe Count of Flanders, Philippe II King of France claimed in 1191 that Flanders escheated to the French crown in default of male heirs on the death of Count Philippe. The settlement was mediated by the Archbishop of Reims and formalised in the Treaty of Arras[309]. Comte Baudouin was eventually enfeoffed as BAUDOUIN VIII Count of Flanders 1 Mar 1192, by right of his wife, on payment of 5,000 silver marks to the French king and doing homage to Emperor Heinrich VI King of Germany for the imperial part of Flanders[310]. On the death of his wife in 1194, Baudouin lost Flanders which was inherited by their oldest son. The necrology of Brogne records the death "XVI Kal Jan" of "Balduinus comes Hannonie"[311].
m (Apr 1169) as her second husband, MARGUERITE de Flandre, widow of RAOUL [II] Comte de Vermandois, daughter of THIERRY I Count of Flanders & his second wife Sibylle d'Anjou ([1145]-15 Nov 1194). The Chronicon Hanoniense records the marriage "tempore Paschali mense April 1169" of "Balduinus" and "Margharetam…Mathie comitis Boloniensis sororem"[312]. She succeeded her brother in 1191 as MARGUERITE I Ctss of Flanders. The necrology of Brogne records the death "XV Kal Dec" of "Margareta comitissa Hainonensis"[313].
Count Baudouin VIII & his wife had seven children