Ferdinand I of Austria

He was both feeble-minded and sexually dysfunctional, placed on the throne by Metternich, cynically, as a puppet for Metternich's own purposes. His marriage to Maria Anna of Sardinia was never consummated, nor did he have any other liaison -- he would not have been capable of it. He is famous for his one coherent command, when someone tried to keep him from eating dumplings because his digestion could not stand it: "I'm the Emperor, and I'll have dumplings."