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.
Friedrich Wilhelm I, Duke of Saxe-Weimar
Friedrich Wilhelm I( 25 April 1562 in Weimar – 7 July 1602 in Weimar) was a duke of Saxe- Weimar.
He was the eldest son of Johann Wilhelm, Duke of Saxe- Weimar and Dorothea Susanne of Simmern.
Christian, Duke of Oldenburg
Christian, Duke of Oldenburg( born 1 February 1955) is the head of the Grand Ducal Family of Oldenburg.
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.
Wilhelm, Duke of Oldenburg
Peter Friedrich "Wilhelm", Duke of Oldenburg (3 January 1754 in Eutin Castle, Eutin – 2 July 1823 in Schloss Plön, Plön.)
Wilhelm succeeded his father, Frederick Augustus
I, Duke of Oldenburg as the Duke of Oldenburg in 1785.
Wilhelm's mother was Princess Ulrike Friederike Wilhelmine of Hesse-Kassel.
Due to mental illness, Wilhelm was duke in name only, with his cousin Peter, Prince-Bishop of Lübeck, acting as regent throughout his entire reign.
The title became a Grand Duke in 1815, but Wilhelm never used the elevated style.
It was not used until 1829 by the son of Wilhelm's cousin and successor, Peter I.
John II, Count of Oldenburg
John II of Oldenburg (died c. 1314 or 1316) was Count of Oldenburg from 1275 until around 1301.
He was the son of Christian III, Count of Oldenburg and Hedwig von Oldenburg in Wildeshausen.
John married twice.
His first marriage was to Elisabeth, the daughter of John, Duke of Brunswick and Lunenburg and Liutgard von Holstein-Itzehoe.
His second marriage was to Countess Hedwig of Diepholz.
John had five children:
John II of Oldenburg is also the patriline ancestor of Queen Margrethe II of Denmark, Philip, Duke of Edinburgh, and thus of Charles, Prince of Wales and Prince William, Duke of Cambridge.
Johann Philipp, Duke of Saxe-Altenburg
Johann Philipp( 25 January 1597 – 1 April 1639), was a duke of Saxe- Altenburg.
He was born in Torgau, the eldest( but fourth in order of birth) surviving son of Friedrich Wilhelm I, Duke of Saxe- Weimar and Anna Maria of the Palatinate- Neuburg, his second wife.
Princess Ulrike Friederike Wilhelmine of Hesse-Kassel
Princess Ulrike Friederike Wilhelmine of Hesse-Kassel  (31 October 1722, Kassel – 28 February 1787, Eutin) was a member of the House of Hesse-Kassel by birth, and of the House of Holstein-Gottorp through her marriage to Frederick Augustus
I, Duke of Oldenburg.
Ulrike was the Duchess consort of Oldenburg from 1774 until her husband's death on 6 July 1785.
Friedrich Wilhelm, Duke of Saxe-Meiningen
Friedrich Wilhelm, Duke of Saxe- Meiningen( 16 February 1679 in Ichtershausen – 10 March 1746 in Meiningen), was a duke of Saxe- Meiningen.
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.

Question: When was Wilhelm, Duke Of Oldenburg's mother born?
Answer: 31 October 1722