Blois

The House of Blois grew from Theobald the Elder, viscount of Tours and Blois in the early tenth century. His descendants stacked up the counties of Blois and Chartres, and from the eleventh century added Troyes and Meaux, the core of Champagne.

Stephen of Blois, William the Conqueror's grandson on his mother's side, seized the English crown in 1135 and held it until 1154. Count Theobald IV of Champagne inherited Navarre in 1234 as King Theobald I; the Blois-Navarre line ruled until Queen Joan I died in 1305, when Navarre and Champagne passed to her husband, Philip IV of France. The Blois-Chartres branch had already died out in 1249, leaving Blois to the Chatillon family.

By 1337 only the counts of Sancerre survived, their hilltop county twice repelling English attacks in the Hundred Years' War even though the Black Prince wasted the country around it. This last line ended with Countess Margaret of Sancerre in 1419, leaving the whole house extinct.