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.
Prince William of Hesse-Kassel
Prince William of Hesse- Kassel( 24 December 1787 – 5 September 1867), was the first son of Prince Frederick of Hesse- Kassel and Princess Caroline of Nassau- Usingen.
Margravine Hedwig Sophie of Brandenburg
Hedwig Sophia of Brandenburg( 14 July 1623, Berlin- 26 June 1683, Schmalkalden) was Landgravine consort of Hesse- Kassel by marriage to William VI, Landgrave of Hesse- Kassel, and regent from 1663 until 1677 during the minority of her sons, William VII, Landgrave of Hesse- Kassel and Charles I, Landgrave of Hesse- Kassel.
William VII, Landgrave of Hesse-Kassel
William VII of Hesse- Kassel( 21 June 1651 – 21 November 1670) was Landgrave of Hesse- Kassel.
Landgravine Marie Louise of Hesse-Kassel
Marie Louise of Hesse-Kassel (7 February 1688 – 9 April 1765) was a Dutch regent, Princess of Orange by marriage to John William Friso, Prince of Orange, and regent of the Netherlands during the minority of her son and her grandson.
She was a daughter of Charles I, Landgrave of Hesse-Kassel, and Maria Amalia of Courland.
She and her husband are the most recent common ancestors of all currently reigning monarchs in Europe.
Marie Louise is notable for having served as regent for two periods in Dutch history: during the reigns of her young son, William IV, Prince of Orange from 1711 and 1730, and of her young grandson, William V, Prince of Orange, from 1759 to 1765.
She was often fondly referred to as Marijke Meu (Aunt Mary) by her Dutch subjects.
George Charles of Hesse-Kassel
George Charles of Hesse-Kassel (8 January 1691 – 5 March 1755) was a prince of Hesse-Kassel and a Prussian General.
Maria Amalia of Courland
Maria Anna Amalia of Courland (12 June 1653 – 16 June 1711) was a Landgravine of Hesse-Kassel through her marriage on 21 May 1673 to her first cousin Charles I, Landgrave of Hesse-Kassel.
She was the child of Jacob Kettler and Margravine Louise Charlotte of Brandenburg, eldest daughter of George William, Elector of Brandenburg.
Charles I, Landgrave of Hesse-Kassel
Charles of Hesse- Kassel( 3 August 1654 – 23 March 1730), of the House of Hesse, was the Landgrave of Hesse- Kassel from 1670 to 1730.
Princess Marie of Hesse-Kassel
Princess and Landgravine Marie of Hesse- Kassel( 21 January 1796 – 30 December 1880) was the consort of George, Grand Duke of Mecklenburg- Strelitz.
Princess Elisabeth of Hesse-Kassel
Princess Charlotte" Elizabeth" Alexandra Mary Louise of Hesse- Kassel( 13 June 1861 – 7 June 1955), was a Princess of Hesse- Kassel by birth and, by her marriage to Leopold, Hereditary Prince of Anhalt, the Hereditary Princess of Anhalt.

Question: Who is Landgravine Marie Louise Of Hesse-Kassel's maternal grandfather?
Answer: Jacob Kettler