Frederick XI, Count of Hohenzollern
Friedrich XI, Count of Hohenzollern( died 26 November 1401), nicknamed" Friedrich the Elder" was a German nobleman.
He was a member of the House of Hohenzollern and a ruling Count of Hohenzollern- Hechingen.
Prince Karl Anton of Hohenzollern
Prince Karl Anton of Hohenzollern- Sigmaringen( 1 September 1868 – 21 February 1919) was a member of the Princely House of Hohenzollern- Sigmaringen.
Karl Anton was the third and youngest son of Leopold, Prince of Hohenzollern and his wife Infanta Antónia of Portugal.
Karl Anton's elder brothers were William, Prince of Hohenzollern and Ferdinand I of Romania.
Prince Hubertus of Hohenzollern
Prince Hubertus of Hohenzollern( Hubertus Gustav Adolf Veit Georg Meinrad Maria Alexander)( born 10 June 1966) is the third child of Prince Johann Georg of Hohenzollern and of his wife Princess Birgitta of Sweden, sister of King Carl XVI Gustaf of Sweden.
Hubertus was born in Munich, Germany.
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.
Johann, Prince of Hohenzollern-Sigmaringen
Prince Johann of Hohenzollern- Sigmaringen( 17 August 1578 in Sigmaringen – 22 March 1638 in Munich), was the ruling Count of Hohenzollern- Sigmaringen from 1606 to 1623.
He was elevated to the rank of prince in 1623 and so was" Prince" of Hohenzollern- Sigmaringen from 1623 until his death.
Princess Margarete Karola of Saxony
Princess Margarete Karola Wilhelmine Viktoria Adelheid
Albertine Petrusa Bertram Paula, Duchess of Saxony (24 January 1900 – 16 October 1962) was the fifth child and second-eldest daughter of Frederick Augustus III of Saxony and his wife Archduchess Luise of Austria, Princess of Tuscany and a younger sister of Georg, Crown Prince of Saxony and Friedrich Christian, Margrave of Meissen.
She was Princess of Hohenzollern from 22 October 1927 until 16 October 1962.
Frederick XII, Count of Hohenzollern
Friedrich XII, Count of Hohenzollern, nickname Friedrich the Oettinger( before 1401 – 1443) was a German nobleman.
He was a member of the Swabian branch of the House of Hohenzollern.
His father was Friedrich XI, Count of Hohenzollern; his younger brother and rival was Eitel Friedrich I, Count of Hohenzollern.
Johann Georg, Prince of Hohenzollern-Hechingen
Johann Georg of Hohenzollern- Hechingen( born 1577 in Hechingen; died 28 September 1623 in Hechingen) was the first Prince of Hohenzollern- Hechingen.
Prince Johann Georg of Hohenzollern
Johann Georg, Prince von Hohenzollern ("Johann Georg
Carl Leopold Eitel-Friedrich Meinrad Maria Hubertus Michael"; 31 July 1932 – 2 March 2016) was a German prince, and through his marriage to Princess Birgitta of Sweden, was brother-in-law of King Carl XVI Gustaf of Sweden.
Prince Johann Georg was the sixth child of Frederick, Prince of Hohenzollern
(Heiligendamm 30 August 1891 – Krauchenwies 6 February 1965) and his wife Princess Margarete Karola of Saxony
(Dresden 24 January 1900 – Freiburg im Breisgau 16 October 1962).
Prince Carl Christian of Hohenzollern
Prince Carl Christian of Hohenzollern( born 5 April 1962) is the eldest child of Prince Johann Georg of Hohenzollern and of his wife Princess Birgitta of Sweden, sister of King Carl XVI Gustaf of Sweden.

Question: Who is Prince Johann Georg Of Hohenzollern's maternal grandfather?
Answer: Frederick Augustus III of Saxony