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.
Adolph, Count of Oldenburg-Delmenhorst
Adolph, Count of Oldenburg- Delmenhorst( b. before 1463 – 17 February 1500) was a Count of Oldenburg from 1482 until his death.
Christian II, Count of Oldenburg
Christian II, Count of Oldenburg( died 1233) was a German nobleman.
He was the ruling Count of Oldenburg from 1209 until his death.
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.
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.
John VI, Count of Oldenburg
John VI, Count of Oldenburg (1501 in Oldenburg – 1548 in Bremen) was a Count of Oldenburg.
He was the eldest son of John V, Count of Oldenburg and his wife, Anna of Anhalt-Bernburg.
He was supposed to rule jointly with his younger brothers.
However, his time in office was marked by conflicts between John VI and his co-rulers.
Christian V, Count of Oldenburg
Christian V, Count of Oldenburg( sometimes called" Christian VI"; – after 6 April 1399) was the ruling count of Oldenburg from 1368 until 1398.
He was born sometime before 1347 to Count Conrad I of Oldenburg and Ingeborg of Brunswick.
After his father died in 1368, he ruled Oldenburg jointly with his elder brother Conrad II, and after Conrad II's deaths in 1386, with the latter's son, Maurice II.
He married Agnes of Honstein, and the Danish Royal houses of Oldenburg and Schleswig- Holstein- Sonderburg- Glücksburg descend from him via his son and successor Dietrich, Count of Oldenburg.
Through the dynastic marriages of his descendants, he is an ancestor of many European Royal houses.
Maria Amalia of Nassau-Dillenburg
Maria Amalia of Nassau- Dillenburg( 27 August 1582 – 31 October 1635) was a daughter of John VI, Count of Nassau- Dillenburg and his second wife, Countess Palatine Kunigunde Jakobäa of Simmern.
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.
Christian, Duke of Oldenburg
Christian, Duke of Oldenburg( born 1 February 1955) is the head of the Grand Ducal Family of Oldenburg.

Question: Who is John Vi, Count Of Oldenburg's paternal grandfather?