Another name for Joan was POITIERS.
Europe in the Middle Ages, Robert S Hoyt, 1957, Harcourt Brace & Co, p468:
"...On his death Louis VIII left a will to be executed by his oldest son, (Saint) Louis IX, directing that when his sons came of age his second son should be given Artois, his third son, Alphonse, who married the heiress of Toulouse, should have Poitou, and his youngest son, Charles, whom we shall meet later as King of the Two Sicilies and founder of the Angevin royal house of Naples, was to have Anjou..."
Political History of England 1216-1377, Vol III, T F Tout, 1905, AMS Press,
p34: "...Henry III was eager to win back his inheritance, though Hubert de Burgh had little faith in Poitevin promises, and, conscious of his king's weakness, managed to prolong the truce, untill July 22, 1229. Three months before that, Blanche succeeded in forcing the unfortunate Raymond VII to accept the humiliating treaty of Meaux, which assured the succession to his dominions to her second son Alfonse, who was to marry his daughter and heiress, Joan..."
p62: "...If Poitou were still in the hands of the Count of La Marche and the Viscount of Thouars, the royal seneschals of Beaucaire and Carcassonne after 1229 ruled overa large part of the old dominions of Raymond of Toulouse. In 1237 the treaty of Meaux was further carried out by the marriage of Raymond's daughter and heiress, Joan, to Alfonse, the brother of the French king. In 1241 Alfonse came of age, andLouis at once invested him with Poitou and Auvergne..."
p105: "... The French king promised to hand over to Henry certain districts then held by his brother, Alfonse of Poitiers, and his brother's wife Joan of Toulouse, in the eventof their dominions escheating to the crown by their death without heirs. These regions included Agen and the Agenais, Saintonge to the south of the Charente, and in addition the whole of Quercy, if it could be proved by inquest that it had beengiven by Richard I to his sister Joan, grandmother of Joan of Poitiers as her marriage portion..."
Encyclopaedia Britannica, 1981, Micropaedia, Vol VII, p440, Raymond VII:
"...For failing to suppress the Cathari, however, he was excommunicated (1226), was declared forfeit of his lands, and was subjected to an invasion by King Louis VIII of France. Although the death of Louis (8 Nov 1226) weakened this campaign, Raymond eventually was compelled by a conference at Meaux and theresultant Treaty of Paris (1229) to cede territory to France and to permit the crusade against the Cathari to continue in Languedoc. The treaty also provided for the marriage of Raymond's daughter Joan to Alphonse, brother of Louis IX of France(St Louis), assuring that the French crown would inherit all of Languedoc.
Joan married Prince Alphonse POITOU, son of King Louis FRANCE, VIII and Queen Blanche Castile FRANCE. (Prince Alphonse POITOU was born on 11 Nov 1220 in Paris, Seine, France.)