Duke Friedrich August of Oldenburg
Duke Friedrich August of Oldenburg (11 January 1936 - 9 July 2017) was a member of the House of Holstein-Gottorp.
He is a son of Nikolaus, Hereditary Grand Duke of Oldenburg and Princess Helena of Waldeck and Pyrmont.
Christian, Duke of Oldenburg
Christian, Duke of Oldenburg( born 1 February 1955) is the head of the Grand Ducal Family of Oldenburg.
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.
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.
John V, Count of Oldenburg
John V, Count of Oldenburg and Delmenhorst (also counted as John XIV, including also non-ruling namesake siblings; 1460, Oldenburg – 10 February 1526, Oldenburg) was a member of the House of Oldenburg.
He was the ruling Count of Oldenburg from 1500 to 1526.
His parents were Gerhard VI, Count of Oldenburg and Adelheid of Tecklenburg.
Duke Peter of Oldenburg
Duke Constantine Frederick Peter of Oldenburg( 26 August 1812 in Yaroslavl, Russian Empire – 14 May 1881 in St. Petersburg, Russian Empire) was a Duke of the House of Oldenburg.
He was the grandfather of Duke Peter of Oldenburg as well as grandfather of Grand Duke Nicholas Nikolaevich, General of the Imperial Russian Army during World War I.
His great- great grandson, Nicholas Romanov, was the President of the Romanov Family Association until his death in 2014.
Peter of Oldenburg was a scholar and philanthropist.
He was also noted composer of music.
In 1857 he composed the music for Marius Petipa's ballet" La Rose, la Violette et le Papillon".
The" Pas d' Esclave" from the ballet" Le Corsaire", which is taken from his score for this work, is still heard in theatres all over the world.
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.
Duchess Therese Petrovna of Oldenburg
Duchess Therese Wilhelmine Olga Friederike of Oldenburg (30 March 1852 – 19 April 1883) was the youngest daughter of Duke Peter Georgievich of Oldenburg and his wife Princess Therese of Nassau-Weilburg.
Nikolaus, Hereditary Grand Duke of Oldenburg
Nikolaus, Hereditary Grand Duke of Oldenburg (10 August 18973 April 1970) was the eldest son of Frederick Augustus II, Grand Duke of Oldenburg, who was the last ruling Grand Duke of Oldenburg.
In 1931, Nikolaus succeeded to his father's titles and assumed the role of pretender to the Grand Duchy, until his death in 1970.
Anton-Günther, Duke of Oldenburg
Anton- Günther, Duke of Oldenburg"( Anton- Günther Friedrich August Josias von Holstein- Gottorp, Erbgroßherzog von Oldenburg, Prinz von Lübeck,;" 16 January 1923 – 20 September 2014) was the head of the Grand Ducal Family of Oldenburg.
He was born in Lensahn the son of Hereditary Grand Duke Nikolaus of Oldenburg( 1897 – 1970) and his first wife Princess Helena of Waldeck and Pyrmont( 1899 – 1948).
Duke Anton- Günther was a grandson of Frederick Augustus II, the last Grand Duke of Oldenburg, and through his mother a grandson of Friedrich, the last Prince of Waldeck and Pyrmont.
He studied for a Diplom in Forestry and succeeded as head of the Grand Ducal Family of Oldenburg upon the death of his father, the Hereditary Grand Duke, on 3 April 1970.
He died in September 2014 aged 91.

Question: Who is Duke Friedrich August Of Oldenburg's paternal grandfather?