Princess Sophie of Saxe-Hildburghausen
Princess Sophie of Saxe- Hildburghausen( Ernestine Friederike Sophie; 22 February 1760, Hildburghausen – 28 October 1776, Coburg), was a Princess of Saxe- Hildburghausen by birth, and by marriage she became the Hereditary Princess of Saxe- Coburg- Saalfeld.
John Ernest IV, Duke of Saxe-Coburg-Saalfeld
Johann Ernest IV, Duke of Saxe- Coburg- Saalfeld( 22 August 1658 in Gotha – 17 February 1729 in Saalfeld) was a reigning duke of Saxe- Coburg- Saalfeld.
Francis Josias, Duke of Saxe-Coburg-Saalfeld
Francis Josias, Duke of Saxe- Coburg- Saalfeld( 25 September 1697, in Saalfeld – 16 September 1764, in Rodach) was a duke of Saxe- Coburg- Saalfeld.
Princess Sophia Wilhelmina of Saxe-Coburg-Saalfeld
Princess Sophia Wilhelmina of Saxe- Coburg- Saalfeld( 9 August 1693, in Saalfeld – 4 December 1727, in Rudolstadt) was a Princess of Saxe- Coburg- Saalfeld by birth, and Princess of Schwarzburg- Rudolstadt by marriage.
Princess Charlotte Sophie of Saxe-Coburg-Saalfeld
Princess Charlotte Sophie of Saxe-Coburg-Saalfeld, Duchess in Saxony (24 September 1731 – 2 August 1810) was a German duchess.
She was the daughter of Franz Josias, Duke of Saxe-Coburg-Saalfeld and Princess Anna Sophie of Schwarzburg-Rudolstadt.
Through his brother Ernest Frederick, Duke of Saxe-Coburg-Saalfeld, she was grandaunt of King Leopold I of Belgium and great-grandaunt of King Leopold II of Belgium, Empress Carlota of Mexico, Queen Victoria of the United Kingdom and her consort Prince Albert.
Princess Sophie of Saxe-Coburg-Saalfeld
Princess Sophie Friederike Karoline Luise of Saxe- Coburg- Saalfeld( 19 August 1778 – 9 July 1835) was a princess of Saxe- Coburg- Saalfeld, and the sister of Princess Victoria of Saxe- Coburg- Saalfeld and King Leopold I of Belgium, and aunt of Queen Victoria.
By marriage, she was a Countess of Mensdorff- Pouilly.
She was born in Coburg, the eldest child of Francis, Duke of Saxe- Coburg- Saalfeld and Countess Augusta Reuss of Ebersdorf.
Ernest Frederick, Duke of Saxe-Coburg-Saalfeld
Ernest Frederick, Duke of Saxe- Coburg- Saalfeld( 8 March 1724 in Saalfeld – 8 September 1800 in Coburg), was a Duke of Saxe- Coburg- Saalfeld.
Princess Juliane of Saxe-Coburg-Saalfeld
Princess Juliane Henriette Ulrike of Saxe-Coburg-Saalfeld (Coburg, 23 September 1781 – Elfenau, near Bern, Switzerland, 15 August 1860), also known as Grand Duchess Anna Feodorovna of Russia , was a German princess of the ducal house of Saxe-Coburg-Saalfeld (after 1826, the house of Saxe-Coburg-Gotha) who became the wife of Grand Duke Konstantin Pavlovich of Russia.
Christian Ernest II, Duke of Saxe-Coburg-Saalfeld
Christian Ernst II, Duke of Saxe-Coburg-Saalfeld (Saalfeld, 18 August 1683 – Saalfeld, 4 September 1745), was a duke of Saxe-Coburg-Saalfeld.
Princess Anna Sophie of Schwarzburg-Rudolstadt
Princess Anna Sophie of Schwarzburg-Rudolstadt (9 September 1700 – 11 December 1780) was a Princess of Schwarzburg-Rudolstadt.
She was the daughter of
Louis Frederick I, Prince of Schwarzburg-Rudolstadt (15 October 1667 – 24 June 1718) and Anna Sophie of Saxe-Gotha-Altenburg (1670–1728).

Question: Who is the maternal grandfather of Princess Charlotte Sophie Of Saxe-Coburg-Saalfeld?
Answer: Louis Frederick I, Prince of Schwarzburg-Rudolstadt