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.
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.
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.
Otto I, Count of Oldenburg
Otto I, Count of Oldenburg( born ca. 1175; died 1251) was Count of Oldenburg from 1209.
His father was Maurice, Count of Oldenburg who died in 1209, whereupon Otto succeeded to the title along with his brother Christian II, Count of Oldenburg.
He participated in the Stedinger Crusade in 1234.
In so doing he won Moorriem, Holle, and Elsfleth from Stedingen and freed himself from the archiepiscopal sovereignty.
He also waged war on County of Hoya and on the Bishopric of Münster, the latter on a dispute over fief.
In 1244 he endowed Menslage- Börstel Monastery.
He was married to Mechthild von Woldenberg with whom he had a daughter, Salome, who married Gerbert, Count of Stotel.
With the death of his son Heinrich in 1255, this line became extinct.
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.
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.
Prince Eitel Friedrich of Prussia
Prince Wilhelm Eitel Friedrich Christian Karl of Prussia (7 July 1883 – 8 December 1942) was the second son of Emperor Wilhelm II of Germany by his first wife, Augusta Viktoria of Schleswig-Holstein.
He was born and died in Potsdam, Germany.
Duchess Sophia Charlotte of Oldenburg
Duchess Sophia Charlotte of Oldenburg (2 February 1879 – 29 March 1964) was a member of the House of Holstein-Gottorp.
She was the only surviving child of Frederick Augustus II, Grand Duke of Oldenburg by his first wife Princess Elisabeth Anna of Prussia.
Sophia Charlotte ("Lotte") is best known for her unhappy and well-publicized marriage to Prince Eitel Friedrich, second son of Wilhelm II, German Emperor.
The marriage later led to divorce; Sophia Charlotte would remarry a few years later to Harald van Hedemann, a former police officer.
Christian, Duke of Oldenburg
Christian, Duke of Oldenburg( born 1 February 1955) is the head of the Grand Ducal Family of Oldenburg.
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.

Question: Where was the husband of Duchess Sophia Charlotte Of Oldenburg born?
Answer: Potsdam