Duke Alexander Petrovich of Oldenburg (2 June 1844 - 6 September 1932) was the second son of Duke Peter Georgievich of Oldenburg and his wife Princess Therese of Nassau-Weilburg. Though he had a German title and ancestry, Alexander and his siblings were born and raised in St. Petersburg as the grandchildren of Grand Duchess Catherine Pavlovna of Russia.

Alexander served as Adjutant general to Alexander III of Russia, and also as commanding general of the Imperial Guard. Alexander was the Russian candidate submitted to succeed Alexander, Prince of Bulgaria, though this nomination failed to gain the support of the other great European powers. At the outbreak of World War I, Nicholas II of Russia appointed Alexander, a medical doctor, as supreme chief of the medical service of the military and naval forces.

Alexander and his wife Princess Eugenia Maximilianovna of Leuchtenberg were noted for their philanthropy, establishing schools, hospitals, orphanages, and other charitable organizations in Russia. During World War I, the duke famously invited wounded British and French soldiers to stay for free in a sanatorium he founded in the Crimea. When the Russian revolution broke out, Alexander was reported to have been one of the Imperial family killed by the newly emerged Bolshevik government, though this turned out to be only a rumor as the duke was able to escape and hide away in Finland and eventually to France, where he died at Biarritz on 6 September 1932.

...
Wikipedia