Prince Friedrich Leopold of Prussia
Joachim Karl Wilhelm
Friedrich Leopold Prinz von Preußen (14 November 1865 in Berlin – 13 September 1931 Krojanke manor, Landkreis Flatow, Posen-West Prussia) was a son of Prince Frederick Charles of Prussia and Princess Maria Anna of Anhalt-Dessau, married in 1854.
Prince Friedrich Karl of Prussia (1828–1885)
Prince Friedrich Karl of Prussia (20 March 1828 – 15 June 1885) was the son of Prince Charles of Prussia (1801–1883) and his wife, Princess Marie of Saxe-Weimar-Eisenach (1808–1877).
Prince Friedrich Karl was a grandson of King Frederick William III of Prussia and a nephew of Frederick William IV and William I.
He was born at Schloss Klein in Berlin.
As a military commander, the Prince had a major influence on the Royal Prussian Army's advances in training and tactics in the 1850s and 1860s.
He defeated the Austrian army at the Battle of Königgrätz in 1866 and the French Army of the Rhine at the Battle of Mars-la-Tour, overseeing the extinction of the Army of the Rhine at the Siege of Metz in 1870.
Prince Friedrich Sigismund of Prussia (1891–1927)
Prince Joachim Viktor Wilhelm Leopold Friedrich Sigismund of Prussia( 17 December 1891 – 6 July 1927) was a German World
War I fighter pilot and member of the House of Hohenzollern.
He was the son of Prince Friedrich Leopold of Prussia and Princess Louise Sophie of Schleswig- Holstein- Sonderburg- Augustenburg, married in 1916.
Prince Friedrich Wilhelm of Prussia
Prince Friedrich Wilhelm of Prussia( 12 July 18809 March 1925) was a member of the House of Hohenzollern, great- grandson of Frederick William III of Prussia.
Princess Marianne of Prussia
Princess Marianne of Prussia( 23 August 19131 March 1983) was a member of the House of Hohenzollern, daughter of Prince Friedrich Wilhelm of Prussia.
Princess Victoria Margaret of Prussia
Princess Victoria Margaret Elizabeth Marie Ulrike of Prussia (17 April 1890 – 9 September 1923) was a member of the House of Hohenzollern.
She was the eldest daughter of Prince Friedrich Leopold of Prussia and his wife Princess Louise Sophie of Schleswig-Holstein-Sonderburg-Augustenburg.
She married Prince Heinrich XXXIII Reuss of Köstritz and had two children.
Charles Pickthorn
Major Charles Edward Murray Pickthorn( 20 September 1896 – 3 March 1938) was a British World
War I flying ace credited with five aerial victories.
His fourth victory resulted in the death of Prince Friedrich Karl of Prussia.
Prince Alexander of Prussia
Prince Friedrich Wilhelm Ludwig" Alexander" of Prussia( 21 June 1820 – 4 January 1896) was the eldest child of Prince Frederick of Prussia and his wife, Princess Luise of Anhalt- Bernburg.
Prince Wilhelm of Prussia (1783–1851)
Prince Friedrich Wilhelm Karl of Prussia( July 1783, Berlin – 28 September 1851, Berlin) was the son of Frederick William II of Prussia and Frederika Louisa of Hesse- Darmstadt.
Princess Maria Anna of Anhalt-Dessau
Princess Maria Anna of Anhalt-Dessau (14 September 1837, Dessau – 12 May 1906, Friedrichroda) was a princess from the House of Ascania.
She was the third child of Leopold IV, Duke of Anhalt and Princess Frederica of Prussia.

Question: Who is the maternal grandfather of Prince Friedrich Leopold Of Prussia?
Answer: Leopold IV