Prince Christian of Denmark (1675–1695)
Prince Christian of Denmark and Norway( 25 March 1675 – 27 June 1695) was the third son of Christian V of Denmark and his consort, Charlotte Amalie of Hesse- Kassel, and thus a younger brother of King Frederick IV.
He died aged 20, and never married.
Prince Christian of Schaumburg-Lippe (1898–1974)
Prince Christian of Schaumburg- Lippe( 20 February 1898 – 13 July 1974) was a German prince and head of the Náchod branch of the princely house of Schaumburg- Lippe.
He was born in Sopron, Hungary, the only son and second child of Frederick of Schaumburg- Lippe( 1868 – 1945) and his first wife Princess Louise of Denmark, younger sister of King Christian X of Denmark.
Moritz, Landgrave of Hesse
Moritz, Prince and Landgrave of Hesse(" Moritz Friedrich Karl Emanuel Humbert" 6 August 1926 – 23 May 2013) was the son of Prince Philip, Landgrave of Hesse, and the head of the House of Brabant and the German House of Hesse.
Prince Waldemar of Schaumburg-Lippe
Prince Waldemar Stephen of Schaumburg- Lippe(" Waldemar Stephan Ferdinand Wolrad Friedrich Karl", b. 19 December 1940 in Glienicke) is a son of Prince Christian of Schaumburg- Lippe and Princess Feodora of Denmark, and the great- grandson of King Frederick VIII of Denmark.
Christian of Oliva
Christian of Oliva, also Christian of Prussia( died 4 December 1245) was the first missionary bishop of Prussia.
Princess Feodora of Denmark
Princess Feodora of Denmark( Feodora Louise Caroline- Mathilde Viktoria Alexandra Frederikke Johanne)
( 3 July 1910 – 17 March 1975) was a Danish princess as a daughter of Prince Harald of Denmark and granddaughter of Frederick VIII of Denmark.
As the wife of Prince Christian of Schaumburg- Lippe she became a Princess of Schaumburg- Lippe by marriage.
Princess Louise of Denmark (1750–1831)
Princess Louise of Denmark and Norway  (20 January 1750 – 12 January 1831) was born to Frederick V of Denmark and Louise of Great Britain.
Her eldest daughter, Marie of Hesse-Kassel, was the wife of Frederick VI of Denmark.
Prince Christian of Hesse-Philippsthal-Barchfeld
Prince Christian of Hesse ("Christian Ludwig Friedrich Adolf Alexis Wilhelm Ferdinand"; 16 June 1889 – 19 October 1971) was a member of the House of Hesse-Philippsthal-Barchfeld and a German naval officer until he resigned his commission during World War I in protest at Germany's policy of unrestricted submarine warfare.
As a member of the House of Hesse, he was styled "His Highness Prince Christian of Hesse".
In order to distinguish between the various branches of the house, the designation "-Philippsthal-Barchfeld" was sometimes added to the end of the princely title.
Alessandra de Osma
Alessandra, Princess Christian of Hanover( née Alessandra de Osma) is a Peruvian attorney, handbag designer, and former model.
She is a member of the Hanoverian royal family through her marriage to Prince Christian of Hanover.
Prince Christian of Hesse
Prince Christian of Hesse  (14 August 1776 – 14 November 1814) was a German prince and member of the House of Hesse-Kassel.
As a son of the Danish Field Marshal Prince Charles of Hesse-Kassel and Princess Louise of Denmark, he was a member of the extended Danish Royal Family and spent his entire life in Denmark.

Question: Who is the maternal grandfather of Prince Christian Of Hesse?
Answer: Frederick V of Denmark