Duke Alexander Petrovich of Oldenburg
Duke Alexander Friedrich Konstantin Petrovich of Oldenburg (Alexander Petrovich Oldenburgsky; 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.
Duke Peter Alexandrovich of Oldenburg
Peter Alexandrovich of Oldenburg (Duke Peter Friedrich Georg von Oldenburg) (21 November 1868 – 11 March 1924) was the first husband of Grand Duchess Olga Alexandrovna of Russia, the youngest sister of Tsar Nicholas II.
Auguste, Duke of Leuchtenberg
Auguste Charles Eugène Napoléon, Duke of Leuchtenberg( 9 December 1810 – 28 March 1835) was the first prince consort of Maria II of Portugal.
Besides being the 2nd Duke of Leuchtenberg and 2nd Prince of Eichstätt, he also held the Brazilian noble title of Duke of Santa Cruz.
Robert W. Levering
Robert Woodrow Levering( October 3, 1914 – August 11, 1989) was a U.S. Representative from Ohio, son-in- law of Usher L. Burdick and brother- in- law of Quentin N. Burdick.
Princess Maria Maximilianovna of Leuchtenberg
Princess Maria Maximilianovna of Leuchtenberg, also known as Princess Maria Romanovskya, Maria, Princess Romanovskaja, Maria Herzogin von Leuchtenberg or Marie Maximiliane( 16 October 1841 – 16 February 1914) was the eldest daughter of Maximilian de Beauharnais, 3rd Duke of Leuchtenberg and his wife Grand Duchess Maria Nikolaevna of Russia.
She married Prince Wilhelm of Baden.
The couple's son, Prince" Maximilian" of Baden, was Germany's last Imperial chancellor.
Princess Eugenia Maximilianovna of Leuchtenberg
Princess Eugenia Maximilianovna of Leuchtenberg  (1 April 1845 – 4 May 1925) was a daughter of Maximilian de Beauharnais, 3rd Duke of Leuchtenberg and his wife Grand Duchess Maria Nikolaevna of Russia.
Although she was a member of the French House of Beauharnais, she was born and raised in her mother's native country, Russia.
In 1868, she married her distant cousin, Duke Alexander Petrovich of Oldenburg.
The couple had an only child, Duke Peter Alexandrovich of Oldenburg.
Princess Eugenia and her husband were particularly noted for their extensive philanthropy throughout Russia; so much so in fact that by 1914, a newspaper source could claim that "there [were] probably not two who are so universally beloved as the Duke and Duchess of Oldenburg".
Countess Elisabeth of Leuchtenberg
Elisabeth of Leuchtenberg( born: March 1537- died: 6 July 1579 in Dillenburg) was the daughter of Landgrave George III, Landgrave of Leuchtenberg and Margravine Barbara of Brandenburg- Ansbach.
Elisabeth of Oettingen
Elisabeth of Oettingen also known as" Elizabeth of Leuchtenberg"( born:; died: 9 July 1406) was a member of the House of Oettingen- Wallerstein by birth.
She was a Landgravine of Leuchtenberg by marriage and a lady in waiting for Elector Palatine and King of Germany Rupert.
Sergei Georgievich, 8th Duke of Leuchtenberg
Prince Sergei Georgievich Romanowsky, 8th Duke of Leuchtenberg (4 July 1890 – 7 January 1974) was the son of Prince George Maximilianovich Romanowsky, 6th Duke of Leuchtenberg and his second wife Princess Anastasia of Montenegro.
He succeeded his half-brother Alexander Georgievich as Duke of Leuchtenberg from 1942 until his death.
Eugen Maximilianovich, 5th Duke of Leuchtenberg
Eugen Maximilianovich Romanowsky, 5th Duke of Leuchtenberg, Prince Romanowsky (8 February 1847 – 31 August 1901) was a son of Maximilian de Beauharnais, 3rd Duke of Leuchtenberg and Grand Duchess Maria Nikolaevna of Russia Duke of Leuchtenberg.
He succeeded his brother Nicholas Maximilianovich as Duke of Leuchtenberg from 1891 until his death.

Question: Who is Princess Eugenia Maximilianovna Of Leuchtenberg's child-in-law?