The Dampierre family, originally from Champagne, dominated the history of Flanders from the fourth decade of the thirteenth century until the accession of Philip the Bold, duke of Burgundy, in 1384. Their sudden rise to power came with the marriage of one of their number, Guillaume de Dampierre, to Marguerite, younger sister and heiress of Countess Jeanne of Flanders. Although by the tests of mutual loyalty and fertility the marriage was a great success, it remained controversial, because Marguerite had earlier been married to Bouchard d'Avesnes, a marriage that the church had annulled, but from which there survived two sons, legitimated by the pope. It was scarcely surprising that the children of the two marriages should have regarded each other as rivals for the rich inheritance of their mother, who became in 1244 ruler both of Flanders and of Hainault. In 1246 Louis IX tried to impose a settlement on the warring step-siblings, whereby he recognised the legitimacy of the two d'Avesnes sons, Jean and Baudoin, and arranged that they should become the heirs to Hainault while the offspring of the second marriage would succeed Marguerite in Flanders. But the compromise was not popular with either party – or indeed with Marguerite, whose affection was confined to the children of her second marriage.