Arthur Gerald Wellesley, Earl of Mornington, is the great-great-grandson of what  last German Emperor ("Kaiser") and King of Prussia?
Wilhelm II, German Emperor Wilhelm II or William II (German: "Friedrich Wilhelm Viktor Albert von Preußen", English: Frederick William Victor Albert of Prussia; 27 January 18594 June 1941) was the last German Emperor ("Kaiser") and King of Prussia, ruling the German Empire and the Kingdom of Prussia from 15 June 1888 to 9 November 1918. He was the eldest grandchild of the British Queen Victoria and related to many monarchs and princes of Europe.
Kaiser-Wilhelmsland Kaiser-Wilhelmsland was part of German New Guinea (German: "Deutsch-Neuguinea"), the South Pacific protectorate of the German Empire. Named in honour of Wilhelm II, who was the German Emperor and King of Prussia, it included the northern part of present-day Papua New Guinea. From 1884 until 1918, the territory was a protectorate of the German Empire. Kaiser-Wilhelmsland, New Pomerania, the Bismarck Archipelago, the northern Solomon Islands, the Caroline Islands, Palau, Nauru, the Mariana Islands, and the Marshall Islands comprised German New Guinea.