Prince Wolfgang of Hesse
Prince Wolfgang of Hesse-Kassel (or Hesse-Cassel) ("Wolfgang Moritz"; 6 November 1896 – 12 July 1989) was the designated Hereditary Prince of the monarchy of Finland (with the irredentist pretension to Estonia), and as such, already called the Crown Prince of Finland officially until 14 December 1918, and also afterwards by some monarchists.
Wolfgang was born at Castle Rumpenheim, Offenbach am Main.
He was the second-born of a pair of twins, the fourth child and son born to Prince Frederick Charles of Hesse (1868–1940) and Princess Margaret of Prussia (1872–1954).
His maternal uncle was the German Emperor William II.
Wolfgang's father Frederick Charles of Hesse was elected King of Finland on 9 October 1918, to replace his first cousin once removed, the deposed Russian emperor, Nicholas II, who was titled "Grand Duke of Finland".
However, Frederick Charles renounced the throne on 14 December 1918, and the title was never actually held by the family.
Wolfgang would have been his father's heir as King of Finland instead of his elder twin Prince Philipp of Hesse (1896–1980), apparently because Wolfgang was with his parents in 1918 and ready to travel to Finland (where a wedding to a Finnish lady was reportedly being prepared for the coming Crown Prince).
Philipp was on active service and incommunicado at the time.
Wolfgang married on 17 September 1924 Princess Marie Alexandra of Baden (1902–1944), daughter of Prince Maximilian of Baden and Princess Marie Louise of Hanover; they had no children.
Wolfgang adopted his nephew, Prince Karl Adolf of Hesse (born 1937), elder son of his younger brother Christoph who was killed in action in 1943.
At the time of his death in Frankfurt at the age of 92, Wolfgang was the only surviving great-grandchild of Queen Victoria of the United Kingdom who had been born in her lifetime.
Victoria died in 1901 when Wolfgang was four years old.
Diana Guardato
Diana Guardato was a member of the aristocratic Patrician Guardato family, and had three children with King Ferdinand I: Diana Guardato is the 16th- Great Grandmother of His Royal Highness Albert II of Belgium, 15th- Great Grandmother of His Majesty Juan Carlos
I of Spain, 17th- Great Grandmother of Philippe of Belgium, 14th- Great Grandmother of His Majesty Manuel II of Portugal, 16th- Great Grandmother of Grand Duke Henri, as well as many others.
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Anne Denman
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Through a fortunate second marriage with Thomas Aylesbury, she became the grandmother of Lady Anne Hyde, Duchess of York and great- grandmother of Queen Mary II and Queen Anne.
Mona Hopton Bell
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She was the grandmother of the painter Jean H. Bell.
Moritz, Landgrave of Hesse
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She is the grandmother of Akhenaten, and great grandmother of Tutankhamun.
Kaoru Hatoyama
After the elections of 2009, she became more widely known as the grandmother of Prime Minister Yukio Hatoyama and his politician brother Kunio Hatoyama.
Princess Margaret of Prussia
Princess Margaret of Prussia (Margarete Beatrice Feodora; 22 April 1872 – 22 January 1954) was a daughter of Frederick III, German Emperor and Victoria, Princess Royal, and the younger sister of Emperor Wilhelm II and a granddaughter of Queen Victoria.
She married Prince Frederick Charles of Hesse, the elected King of Finland, making her the would-be Queen of Finland
had he not decided to renounce the throne on 14 December 1918.
In 1926 they assumed the titles of Landgrave and Landgravine of Hesse.
She lost three sons in World Wars I and II.

Question: Who is the maternal grandmother of Prince Wolfgang Of Hesse?
Answer: Victoria, Princess Royal