Duke Louis of Württemberg
Duke Louis of Württemberg ("Ludwig Friedrich Alexander")
(Treptow an der Rega, 30 August 1756 – Kirchheim unter Teck, 20 September 1817)
was the second son of Frederick II Eugene, Duke of Württemberg (1732–1797) and Margravine Sophia Dorothea of Brandenburg-Schwedt (1736–1798).
His elder brother was Frederick I, the first King of Württemberg, his sister was the Russian Empress consort, Maria Feodorovna.
Louis retained the pre-royal title of Duke.
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.
Archduchess Maria Dorothea of Austria
Archduchess Maria Dorothea of Austria, full German name: "Maria Dorothea Amalie, Erzherzogin von Österreich"
(Maria Dorothea Amelia; 14 June 1867 – 6 April 1932) was a member of the Hungarian line of the House of Habsburg and an Archduchess of Austria by birth.
Through her marriage to Philippe, Duke of Orléans, Maria Dorothea was also a member of the House of Orléans.
Philippe was the Orléanist claimant to the throne of France from 1894 to 1926 and known to Orléanist monarchists as "Philippe VIII of France."
Thus, to Orléanist monarchists, Maria Dorothea was titular Queen of France from 1896 to 1926, and Dowager Queen of France until her death in 1932.
Duchess Maria Dorothea of Württemberg
Duchess Maria Dorothea of Württemberg (Maria Dorothea Luise Wilhelmine Caroline; 1 November 1797 in Carlsruhe (now Pokój), Silesia – 30 March 1855 in Pest, Hungary) was the daughter of Duke Louis of Württemberg (1756–1817) and Princess Henriette of Nassau-Weilburg (1780–1857).
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.
Archduchess Elisabeth Franziska of Austria
Archduchess Elisabeth Franziska Maria of Austria (17 January 1831 – 14 February 1903) was born in Ofen (Buda), Hungary, the daughter of Palatine Joseph of Hungary (1776–1847) and his third wife Maria Dorothea of Württemberg (1797–1855).
Marie Henriette of Austria
Marie Henriette of Austria (Marie Henriette Anne; 23 August 1836 – 19 September 1902) was Queen of the Belgians as the wife of King Leopold II.
Marie Henriette was one of five children from the marriage of Archduke Joseph, Palatine of Hungary, and Duchess Maria Dorothea of Württemberg.
Marie Henriette was a cousin of Emperor Ferdinand I of Austria, and granddaughter of Leopold II, Holy Roman Emperor, through her father.
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.
Duchess Maria Isabella of Württemberg
Duchess "Maria Isabella" Philippine Theresia Mathilde Josephine of Württemberg  (30 August 1871 – 24 May 1904) was a member of the House of Württemberg and a Duchess of Württemberg by birth and a member of the House of Wettin and a Princess of Saxony through her marriage to Prince Johann Georg of Saxony.
Catherine Pavlovna of Russia
Grand Duchess Catherine Pavlovna of Russia( 21 May 1788[ OS 10 May 1788] – 9 January 1819) later Queen Catharina Pavlovna of Württemberg, was the fourth daughter of Tsar Paul I of Russia and Duchess Sophie Dorothea of Württemberg.
She became the Queen of Württemberg upon her marriage to her first cousin Crown Prince William who eventually became King William I of Württemberg in 1816.

Question: Who is Duchess Maria Dorothea Of Württemberg's paternal grandfather?
Answer: Frederick II Eugene, Duke of Württemberg