Guy I, Count of Blois

Guy I of Châtillon, Count of Blois, son of Hugh II of Châtillon and Beatrix of Dampierre, was Count of Blois and Lord of Avesnes 1307-1342.
In 1310, he married Margaret of Valois, daughter of Charles of Valois and sister of Philip VI of France. They had three children:

Louis II, Count of Blois
Charles of Blois - would marry Joanna, Duchess of Brittany; Charles and the French would engage in the Breton War of Succession against the House of Montfort and the English
Marie of Blois, married in 1334 Rudolph, Duke of Lorraine, married secondly, Count of Leiningen-Dagsburg.

He took part in the expedition of Louis X of France against his uncle Robert III of Flanders in 1315, and in the early stages of the Hundred Years' War.