In 1244, the death of her older sister who had no offspring, Marguerite of Hainaut and of Flanders (also known as Margaret of Constantinople as second daughter of Baldwin VI of Hainaut) inherited Flanders and Hainaut. She was nicknamed the Black for her dishonorable conduct. From her first marriage in Le Quesnoy in 1212, with Bouchard Avesnes, her teacher she had chosen herself, she had two surviving sons, John and Baldwin of Avesnes. She divorced, for reasons unknown (Bouchard belonged, however, to English stock) and married again in 1223, a knight of Champagne, Guillaume de Dampierre who gave her three sons, and she tried to help (them) by bequest and inheritance: what proved the origin of a quarrel that engulfed Hainaut and Flanders. Louis IX of France, King of France, was called to serve as arbitrator: the king, after taking advice, apportioned Flanders to the Dampierres and Hainaut to the Avesnes. However, despite this wise decision, fighting continued between members of two families. In Le Quesnoy and its environs Margaret Hainaut had, in addition to land, a wealth of manorial rights: duties on goods brought to the market, rights on meat and beer sold, rights over the entry and exit of goods; rights over the number of the mills and ovens, rights over products of rivers etc. She preferred to lease it all through an annual fee: between 1274 and 1277, a citizen of Le Quesnoy called Clarembault settled an annual fee of 2925 pounds. Also, a cartulary of the said Margaret tells us that in Le Quesnoy at that time there were about six hundred properties, and they measured up to 33m long and 13m wide on the road; there were nine bread ovens in the town that residents were subjected to forced labor, such as to provide firewood to the castle, but in return, they could collect dead wood; in case of war the call to Quercitains would be twenty-four hours after that to the Valenciennes.