Duchess Frederica of Württemberg
Duchess Frederica of Württemberg( 27 July 1765 – 24 November 1785) was a daughter of Frederick II Eugene, Duke of Württemberg and Friederike Dorothea of Brandenburg- Schwedt.
Princess Friederike of Brandenburg-Schwedt
Friederike of Brandenburg-Schwedt (Friederike Sophia Dorothea; 18 December 1736 – 9 March 1798) was Duchess of Württemberg by marriage to Frederick II Eugene, Duke of Württemberg.
She is an ancestor to many European royals of the 19th and 20th century.
Frederick Augustus, Duke of Württemberg-Neuenstadt
Frederick Augustus of Württemberg-Neuenstadt (Neuenstadt am Kocher, 12 March 1654 – 6 August 1716 in Gochsheim) was Duke of Württemberg and second Duke of Württemberg-Neuenstadt.
Princess Catherine of Württemberg
Princess Catherine Frederica Charlotte of Württemberg (Stuttgart, 24 August 1821 – Stuttgart, 6 December 1898) was a daughter of William I of Württemberg and Pauline Therese of Württemberg.
She was the mother of William II of Württemberg.
Franziska von Hohenheim
Countess Franziska Theresia von Hohenheim( 10 January 1748 in Adelmannsfelden – 1 January 1811 in Kirchheim unter Teck) was a German noblewoman.
From birth she was a baroness von Bernerdin and from 1765 onwards Baroness Leutrum von Ertingen.
She was the official mistress of Charles Eugene, Duke of Württemberg from 1772 to 1785, when she became his second wife.
The marriage was morganatic until 1790, when she was allowed use of the dynastic title" Duchess of Württemberg".
Princess Marie Auguste of Thurn and Taxis
Princess Marie Auguste Anna of Thurn and Taxis (11 August 1706 – 1 February 1756) was a Regent of Württemberg.
She was a member of the Princely House of Thurn and Taxis as a daughter of Anselm Franz, 2nd Prince of Thurn and Taxis and his wife Maria Ludovika Anna Franziska, Princess of Lobkowicz.
Through her marriage to Karl Alexander, Duke of Württemberg, she became Duchess consort of Württemberg.
Charles Eugene, Duke of Württemberg
Charles Eugene (German: "Carl Eugen"; 11 February 1728 – 24 October 1793), Duke of Württemberg, was the eldest son, and successor, of Charles Alexander; his mother was Princess Marie Auguste of Thurn and Taxis.
Prince Frederick of Württemberg
Prince" Frederick" Charles Augustus of Württemberg( 21 February 1808 – 9 May 1870) was a General in the Army of Württemberg and the father of William II of Württemberg.
Frederick was a member of the Royal Family of Württemberg and a Prince of Württemberg.
Duke Alexander of Württemberg (1771–1833)
Duke Alexander of Württemberg
(Mömpelgard/Montbéliard, then Württemberg (now France), 5 May 1771 – Gotha, Thuringia, Germany, 4 July 1833) was a Duke of Württemberg.
The son of Frederick II Eugene, Duke of Württemberg and of Sophia Dorothea of Brandenburg-Schwedt.
His sister Sophie Dorothea married Tsar Paul I of Russia.
Christoph, Duke of Württemberg
Christoph of Württemberg, Duke of Württemberg (12 May 1515 – 28 December 1568) ruled as Duke of Württemberg from 1550 until his death in 1568.

Question: Who is the maternal grandfather of Charles Eugene, Duke Of Württemberg?
Answer: Anselm Franz, 2nd Prince of Thurn and Taxis