Karl Wilhelm, Duke of Saxe-Meiningen
August Friedrich Karl Wilhelm, Duke of Saxe-Meiningen (Frankfurt, 19 November 1754 – Sonneberg, 21 July 1782), was a duke of Saxe-Meiningen.
Bernhard III, Duke of Saxe-Meiningen
Bernhard III, Duke of Saxe- Meiningen( 1 April 1851 – 16 January 1928), was the last reigning duke of Saxe- Meiningen.
Princess Louise Eleonore of Hohenlohe-Langenburg
Princess Luise Eleonore of Hohenlohe- Langenburg( 11 August 1763, in Langenburg – 30 April 1837, in Meiningen) was a German regent.
She was duchess of Saxe- Meiningen by marriage to George I, Duke of Saxe- Meiningen, and Regent of Saxe- Meiningen during the minority of her son from 1803 to 1821.
Bernhard, Prince of Saxe-Meiningen
Bernhard, Prince of Saxe- Meiningen( 30 June 1901 – 4 October 1984) was the head of the House of Saxe- Meiningen from 1946 until his death.
Princess Charlotte of Saxe-Meiningen
Princess Charlotte of Saxe- Meiningen( 11 September 1751, Frankfurt am Main, Free Imperial City of Frankfurt, Holy Roman Empire – 25 April 1827, Genoa, Kingdom of Sardinia) was a member of the House of Saxe- Meiningen and a Princess of Saxe- Meiningen by birth and a member of the House of Saxe- Gotha- Altenburg and Duchess consort of Saxe- Gotha- Altenburg through her marriage to Ernest II, Duke of Saxe- Gotha- Altenburg.
Friedrich Wilhelm, Duke of Saxe-Meiningen
Friedrich Wilhelm, Duke of Saxe- Meiningen( 16 February 1679 in Ichtershausen – 10 March 1746 in Meiningen), was a duke of Saxe- Meiningen.
Princess Marie Frederica of Hesse-Kassel
Princess Marie Frederica Wilhelmina of Hesse-Kassel (6 September 1804 – 1 January 1888) was a Duchess consort of Saxe-Meiningen by marriage to Bernhard II, Duke of Saxe-Meiningen.
She was the daughter of William II, Elector of Hesse and Princess Augusta of Prussia.
Georg, Prince of Saxe-Meiningen
Georg, Prince of Saxe- Meiningen( 11 October 1892 – 6 January 1946) was the head of the house of Saxe- Meiningen from 1941 until his death.
Princess Marie Anne of Saxe-Altenburg
Princess Marie Anne of Saxe- Altenburg( 14 March 1864 – 3 May 1918) was the consort of Georg, Prince of Schaumburg- Lippe.
As the eldest daughter of Prince Moritz of Saxe- Altenburg and his wife Princess Augusta of Saxe- Meiningen, and a sister of Ernest II, Duke of Saxe- Altenburg, Marie Anne was a member of the Ducal House of Saxe- Altenburg.
Princess Augusta of Saxe-Meiningen
Princess Augusta Louise Adelaide Caroline Ida of Saxe-Meiningen (6 August 1843 – 11 November 1919) was the daughter of Bernhard II, Duke of Saxe-Meiningen and his wife Princess Marie Frederica of Hesse-Kassel.
She was the mother of Ernst II, Duke of Saxe-Altenburg.

Question: Who is the maternal grandfather of Princess Augusta Of Saxe-Meiningen?
Answer: William II