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.
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.
Georg von Habsburg
Georg von Habsburg (given names "Paul Georg Maria Joseph Dominikus"; born 16 December 1964, in Starnberg), referred to in Austria as Georg Habsburg-Lothringen, in Hungary as Habsburg György, and by his royal name as Archduke Georg of Austria, is the second son, and seventh and youngest child of Otto von Habsburg, the last Crown Prince of Austria-Hungary, and Princess Regina of Saxe-Meiningen.
Peter Burroughs
Peter Burroughs( born 27 January 1947) is a British television and film actor, the director of Willow Management.
He is the father- in- law of actor and TV presenter Warwick Davis.
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.
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.
Elimar II, Count of Oldenburg
Elimar II( also Egilmar) was Count of Oldenburg from 1108 through 1142.
He was son of Elimar I, Count of Oldenburg and his wife Richenza.
Elimar married before 1102 Eilika of Werl- Rietberg, daughter of Henry, Count of Rietberg.
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.
Ogawa Mataji
Viscount was a general in the early Imperial Japanese Army.
He was also the father- in- law of Field Marshal Gen Sugiyama.

Question: Who is Duchess Eilika Of Oldenburg's father-in-law?
Answer: Otto von Habsburg