Eduard von Habsburg
Eduard von Habsburg( born January 12, 1967), also known as Archduke Eduard of Austria is Hungary ’s ambassador to the Holy See and Sovereign Military Order of Malta.
He is son of Archduke Michael of Austria( Archduke Joseph Francis's youngest child) and the great- great- grandson of Emperor Franz Joseph I.
He is married to Baroness Maria Theresia von Gudenus, descendant of Archduke Johann of Austria and has six children.
Archduke Otto of Austria (1865–1906)
Archduke Otto Franz Joseph Karl Ludwig Maria of Austria (21 April 1865 – 1 November 1906) was the second son of Archduke Karl Ludwig of Austria (younger brother of Emperor Franz Joseph I of Austria) and his second wife, Princess Maria Annunciata of Bourbon-Two Sicilies.
He was the father of Charles I of Austria, the last Emperor of Austria.
Archduchess Elisabeth Amalie of Austria
Archduchess Elisabeth Amalie of Austria (7 July 1878 – 13 March 1960) was a daughter of Archduke Karl Ludwig of Austria and his third wife Infanta Maria Theresa of Portugal.
She was the mother of Franz Joseph II, Prince of Liechtenstein, and the paternal grandmother of Hans-Adam II, Prince of Liechtenstein.
Tjuyu
Tjuyu( sometimes transliterated as Thuya or Thuyu) was an Egyptian noblewoman and the mother of queen Tiye, and the wife of Yuya.
She is the grandmother of Akhenaten, and great grandmother of Tutankhamun.
Archduchess Yolande of Austria
Archduchess Yolande of Austria( née Princesse Yolande Marie Jeanne Charlotte de Ligne; born 6 May 1923) is the widow of Archduke Carl Ludwig of Austria.
Maria Theresa of Austria-Este (1849–1919)
Maria Theresa of Austria-Este (Maria Theresa Henriette Dorothee; 2 July 1849 – 3 February 1919) was the last Queen of Bavaria.
She was the daughter and only child of Archduke Ferdinand of Austria-Este and his wife, Archduchess Elisabeth of Austria.
Hubba bint Hulail
Hubba bint Hulail was the grandmother of Hashim ibn' Abd Manaf, thus the great- great- great- grandmother of the Islamic" Nabī"( Prophet) Muhammad ibn Abdullah.
Hannah Arnold
Hannah Arnold, also known as Hannah Waterman King, was the grandmother of Benedict Arnolds children.
Archduke Stefan of Austria
Archduke Stefan of Austria, Prince of Tuscany  (15 August 1932 in Mödling, Lower Austria, Austria – 12 November 1998 in Brighton, Michigan, United States) was a member of the House of Habsburg an Archduke and Prince of Tuscany by birth.
Stefan was the eldest child and son of Archduke Anton of Austria and his wife Princess Ileana of Romania.
Princess Ileana of Romania
Princess Ileana of Romania, also known as Mother Alexandra (5 January 1909 – 21 January 1991), was the youngest daughter of King Ferdinand I of Romania and his consort, Queen Marie of Romania.
She was a great-granddaughter of Queen Victoria and of Tsar Alexander II.
She was born as "Her Royal Highness" Ileana, Princess of Romania, Princess of Hohenzollern-Sigmaringen.

Question: Who is the maternal grandmother of Archduke Stefan Of Austria?
Answer: Marie of Romania