Conrad I, Count of Oldenburg
Conrad I of Oldenburg (died 1347) was the Count of Oldenburg from 1344 to 1347.
He succeeded his brother, John III of Oldenburg.
He was the son of John II of Oldenburg and Hedwig of Diepholz.
Conrad married Ingeborg, the daughter of Count Gerhard IV of Holstein-Plön.
They had four children:
Conrad I of Oldenburg is also a male-line ancestor of Queen Margrethe II of Denmark, King Harald V of Norway, and of Philip, Duke of Edinburgh, and thus of Charles, Prince of Wales, and Prince William, Duke of Cambridge.
Alexander Skugarev
Alexander Petrovich Skugarev( born 13 March 1975) is a retired Russian professional ice hockey center.
John VII, Count of Oldenburg
Count John VII of Oldenburg and Delmenhorst( nicknamed" the Dike Builder"; 9 September 1540 in Oldenburg – 12 November 1603 in Oldenburg) was a member of the House of Oldenburg and was the ruling Count of County of Oldenburg from 1573 until his death.
His parents were Count Anthony I of Oldenburg and Sophie of Saxe- Lauenburg.
Prince Roman Petrovich of Russia
Prince Roman Petrovich of Russia( 17 October 1896 – 23 October 1978) was a member of the House of Romanov.
Duchess Eilika of Oldenburg
Duchess Eilika of Oldenburg( née Duchess Eilika Helene Jutta Clementine of Oldenburg; born 22 August 1972) is the wife of Georg von Habsburg, the third in the line of succession to the former Austro- Hungarian throne.
She was in line of succession to the British throne before her marriage to a Roman Catholic.
She is a daughter of Duke Johann of Oldenburg and his wife Countess Ilka of Ortenburg.
Her father is a younger son of Nikolaus, Hereditary Grand Duke of Oldenburg and his wife Princess Helena of Waldeck and Pyrmont.
Princess Therese of Nassau-Weilburg
Princess Therese Wilhelmine Friederike Isabelle Charlotte of Nassau-Weilburg, (
Terezya Vasilyevna Nassauskaya; 17 April 1815 in Weilburg, Duchy of Nassau – 8 December 1871 in Prague, Kingdom of Bohemia, Austria–Hungary) was a member of the House of Nassau-Weilburg and a Princess of Nassau-Weilburg by birth.
Through her marriage to Duke Peter of Oldenburg, Therese was also a Duchess of Oldenburg.
Christian, Duke of Oldenburg
Christian, Duke of Oldenburg( born 1 February 1955) is the head of the Grand Ducal Family of Oldenburg.
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".
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.
Anthony I, Count of Oldenburg
Anthony I, Count of Oldenburg and Delmenhorst( 1505 – 22 January 1573, Oldenburg) was a member of the House of Oldenburg and was the Imperial Count of the Counties of Oldenburg and Delmenhorst within the Holy Roman Empire of German Nation.
His parents were John V, Count of Oldenburg( 1460- 1525) and Anna of Anhalt- Zerbst.

Question: When did Duke Alexander Petrovich Of Oldenburg's mother die?