The title, like others in Spain, can pass through an heiress to her husband.
Maria Theresa considered herself first and foremost as the heiress of the rights of the house of Austria.
She was the last heiress of the great house of Canossa, whose fiefs stretched from Mantua across Lombardy, passed the Apennines, included the Tuscan plains, and embraced a portion of the duchy of Spoleto.
About 1120 another Giso, count of Gudensberg, secured possession of the lands of the Werners; on his death in 1137 his daughter and heiress, Hedwig, married Louis, landgrave of Thuringia; and from this date until 1247, when the Thuringian ruling family became extinct, Hesse formed part of Thuringia.
In the meanwhile his son Oddone married Adelaide, eldest daughter and heiress of Odelrico Manfredi, marquess of Susa, a descendant of Arduino of Ivrea, king of Italy, who ruled over the counties of Turin, Auriate, Asti, Bredulo, Vercelli, &c., corresponding roughly to modern Piedmont and part of Liguria (1045).