Princess Luise Dorothea of Saxe-Meiningen
Luise Dorothea of Saxe- Meiningen( 10 August 1710 – 22 October 1767) was a member of German royalty.
She was born in Meiningen, the daughter of Ernst Ludwig I, Duke of Saxe- Meiningen and Dorothea Marie of Saxe- Gotha.
She was the wife of Frederick III, Duke of Saxe- Gotha- Altenburg.
Dorothea of Denmark, Duchess of Prussia
Dorothea of Denmark (1 August 1504 – 11 April 1547), was a Duchess of Prussia by marriage to Duke Albert, Duke of Prussia.
She was the daughter of King Frederick I of Denmark and Anna of Brandenburg.
Princess Charlotte of Prussia (1831–1855)
Princess Charlotte of Prussia( 21 June 1831 – 30 March 1855), was by birth a Princess of Prussia and member of the House of Hohenzollern and by marriage Hereditary Princess of Saxe- Meiningen.
She was the eldest child and daughter of Prince Albert of Prussia( younger son of Frederick William III of Prussia and Louise of Mecklenburg- Strelitz) and his first wife Princess Marianne of the Netherlands( daughter of William I of the Netherlands and Wilhelmine of Prussia).
Princess Luise of Anhalt-Bernburg
Princess Luise of Anhalt- Bernburg( 30 October 1799, Ballenstedt – 9 December 1882, Eller, Düsseldorf) was a German Princess.
As the daughter of Alexius Frederick Christian, Duke of Anhalt- Bernburg and his wife Marie Friederike of Hesse- Kassel, she was a Princess of Anhalt- Bernburg and member of the House of Ascania.
By her 21 November 1817 marriage to Prince Frederick of Prussia she was a princess of Prussia.
She had two children: Prince Alexander of Prussia( 21 June 1820, Berlin – 4 January 1896, Berlin) and Prince George of Prussia( 12 February 1826, Düsseldorf – 2 May 1902, Berlin).
Anna Amalia, Abbess of Quedlinburg
Princess Anna Amalia of Prussia (9 November 1723 – 30 March 1787) was Princess-Abbess of Quedlinburg.
She was one of ten surviving children of King Frederick William I of Prussia and Sophia Dorothea of Hanover.
Princess Friederike Luise of Prussia
Princess Friederike Luise of Prussia( 29 August 1714 – 4 February 1784) was a daughter of Frederick William I of Prussia and Sophia Dorothea of Hanover and Margravine of Brandenburg- Ansbach.
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.
Princess Luise Dorothea of Prussia
Princess Luise Dorothea of Prussia (Luise Dorothea Sophie; 29 September 1680 – 23 December 1705) was Hereditary Princess of Hesse-Kassel by marriage to Frederick, Hereditary Prince of Hesse-Kassel.
She was the daughter of Frederick I, First King in Prussia by his first wife Elisabeth Henriette of Hesse-Kassel.
She died in childbirth.
Elisabeth Henriette of Hesse-Kassel
Landgravine Elisabeth Henriëtte of Hesse-Kassel (18 November 1661 – 7 July 1683) was the daughter of William VI, Landgrave of Hesse-Kassel and Hedwig Sophia of Brandenburg (1623–1683) a sister of Elector Frederick William of Brandenburg.
Princess Sophia Dorothea of Prussia
Princess Sophia Dorothea of Prussia  (25 January 1719 – 13 November 1765) was the ninth child and fifth daughter of Frederick William I of Prussia and Sophia Dorothea of Hanover.
By marriage, she was a Margravine of Brandenburg-Schwedt.

Question: Who is Princess Luise Dorothea Of Prussia's maternal grandfather?
Answer: William VI, Landgrave of Hesse-Kassel