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.
Louis Frederick, Duke of Württemberg-Montbéliard
Louis Frederick of Württemberg- Montbéliard( 29 January 1586 in Montbéliard – 26 January 1631 in Montbéliard) was the founder of a cadet line of the House of Württemberg known as the Dukes of Württemberg- Montbéliard.
Louis Frederick of Württemberg was born at Montbéliard Castle as the fifth child and second son of Duke Frederick I of Württemberg, and princess Sibylla of Anhalt.
Duchess Elsa of Württemberg
Duchess Elsa of Württemberg (Elsa Mathilde Marie; 1 March 1876 – 27 May 1936) was a daughter of Duke Eugen of Württemberg and Grand Duchess Vera Constantinovna of Russia.
She married Prince Albert of Schaumburg-Lippe.
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.
Duke Carl Alexander of Württemberg
Carl Alexander Herzog von Württemberg( Father Odo OSB)( 12 March 1896 – 27 December 1964) was a member of the House of Württemberg who became a Benedictine monk.
(" Herzog von Württemberg" is German for" Duke of Württemberg".)
During, and following, the Nazi era he provided aid to refugees, Jews, and prisoners of war, and was reported for these activities to the Nazi rulers of Germany.
Pauline Therese of Württemberg
Pauline of Württemberg (4 September 1800 – 10 March 1873) was a daughter of Duke Louis of Württemberg and Princess Henriette of Nassau-Weilburg.
She married her first cousin King William I of Württemberg and was his consort.
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.
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.
Princess Augusta of Württemberg
Princess Augusta of Württemberg( 4 October 1826 in Stuttgart – 3 December 1898, ibid.) was a daughter of King William I of Württemberg and his wife, Pauline of Württemberg.
Duke Eugen of Württemberg (1846–1877)
Duke Eugen of Württemberg (20 August 1846 – 27 January 1877) was a German prince and a staff officer of Württemberg.

Question: What nationality is Duchess Elsa Of Württemberg's father?
Answer: German