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.
Ludwig Windthorst Baron Ludwig Windthorst (17 January 1812 – 14 March 1891), was a German politician and leader of the Catholic Centre Party, the most notable opponent of Chancellor Otto von Bismarck during the Prussian-led unification of Germany and the Kulturkampf. Anderson argues that he was "Imperial Germany's greatest parliamentarian," one who bears comparison with Irishmen Daniel O'Connell and Charles Stewart Parnell "in his handling of party machinery and his relation to the masses."