Thibaut I

…of count was assumed by Thibaut I the Old, or the Cheat (d. c. 977), who founded the hereditary house of Blois. He enlarged his domain until it extended from the Indre River to the Eure.

…hands until about 940, when Theobald I (the Old) seized control of it and founded a line of counts of Blois. His successors, notably the fearsome Eudes II (996–1037), annexed the counties of Sancerre (1015) and Champagne (1019–23), thereby creating a principality comparable in strength to Flanders and more threatening…