Württemberg-Hohenzollern
After World War the Kingdom of Württemberg became the Free Peoples' State of Württemberg. After World War II the part of the Free Peoples' State of Württemberg and the old Principality of Hohenzollern were joined to make Württemberg-Hohenzollern. The name of the Royal family of Prussia was Hohenzollern because they came from this area. This is also why it was always part of Prussia until Prussia was abolished after World War II.