Louis of Evreux was married once, to Marguerite of Artois, a great-granddaughter of Henry III of England via her mother Blanche of Brittany and Blanche's mother Beatrice, who was the second daughter of Henry III and Eleanor of Provence. Marguerite's father Philip would have succeeded their father Robert (younger brother of Blanche of Artois, queen of Navarre, Queen Isabella's maternal grandmother) as count of Artois, but he died in 1298 before his father, and Artois passed to Philip's sister Mahaut (mother of Joan and Blanche of Burgundy who married Queen Isabella's brothers Philip V and Charles IV) rather than his son, Marguerite's younger brother Robert (1287-1342). This Robert was the son-in-law of Charles of Valois, and the brother-in-law of Charles of Valois's half-brother Louis of Evreux. Louis's wife Marguerite of Artois was the first cousin of Joan and Blanche of Burgundy, who were Louis's nieces by marriage, wives of Queen Isabella's brothers Philip (V) and Charles (IV). The French royal family in the early fourteenth century was extremely, madly and confusingly inter-related; if I've worked it out correctly, Marguerite of Artois was the first cousin once removed of Edward II and the second cousin of Queen Isabella.
Charles of Valois was married three times. His first wife was Marguerite of Anjou-Naples (1273-1299), countess of Anjou in her own right, one of the children of Charles of Salerno, king of Naples and Marie of Hungary; her many siblings included Charles Martel, titular king of Hungary, Robert, king of Naples and titular king of Sicily and Jerusalem, Philip, king of Albania, Saint Louis, bishop of Toulouse, and Blanche, queen of Jaime II of Aragon. Charles of Valois married secondly Catherine de Courtenay (1274-1307), titular empress of Constantinople in her own right and a first cousin of Charles' first wife Marguerite, and thirdly Mahaut de Châtillon (1293-1358), daughter of the count of St Pol and older sister of Marie, countess of Pembroke. Mahaut was, like her first cousin Marguerite of Artois above, a great-granddaughter of Henry III and Eleanor of Provence. Charles of Valois and Marguerite of Anjou-Naples were the maternal grandparents of Edward III's queen Philippa of Hainault, and the parents of Philip VI of France.
In the second part of this post, I'll be looking at the children of Charles of Valois and Louis of Evreux. Coming soon!