Question: Who is Robert, Archduke Of Austria-Este's maternal grandfather?

Princess Elisabetta of Belgium
Princess Elisabetta of Belgium, Archduchess of Austria- Este( née" Nob." Elisabetta Rosboch von Wolkenstein on 9 September 1987) is the wife of Prince Amedeo of Belgium, Archduke of Austria- Este.
Prince Joachim of Belgium, Archduke of Austria-Este
Prince Joachim of Belgium, Archduke of Austria- Este(" Joachim Karl- Maria Nikolaus Isabelle Marcus d' Aviano"; born 9 December 1991), is the younger son and third child of Lorenz, Archduke of Austria- Este and Princess Astrid of Belgium.
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.
Princess Luisa Maria of Belgium, Archduchess of Austria-Este
Princess Luisa Maria of Belgium, Archduchess of Austria- Este( Luisa Maria Anna Martine Pilar; born 11 October 1995) is the fourth child and second daughter of Lorenz, Archduke of Austria- Este, and Princess Astrid of Belgium.
She was born at the Saint Jean Hospital in Brussels, Belgium, and is currently ninth in line to the Belgian throne.
Maria Ludovika of Austria-Este
Maria Ludovika of Austria- Este, also known as Maria Ludovika of Modena,( 14 December 1787 – 7 April 1816) was the daughter of Archduke Ferdinand of Austria- Este( 1754 – 1806) and his wife, Maria Beatrice Ricciarda d' Este( 1750 – 1829).
She was a member of the House of Austria- Este, a branch of the House of Habsburg- Lorraine.
Robert, Archduke of Austria-Este
Archduke Robert, Archduke of Austria-Este (8 February 1915 – 7 February 1996), was the second son of Karl I, (beatified)
last Emperor of Austria-Hungary, and Princess Zita of Bourbon-Parma.
Zita of Bourbon-Parma
Zita of Bourbon-Parma ("Zita Maria delle Grazie Adelgonda Micaela Raffaela Gabriella Giuseppina Antonia Luisa Agnese"; 9 May 1892 – 14 March 1989) was the wife of Charles, the last monarch of Austria-Hungary.
As such, she was the last Empress of Austria and Queen of Hungary, in addition to other titles.
Born as the seventeenth child of the dispossessed Robert I, Duke of Parma, and his second wife, Infanta Maria Antonia of Portugal, Zita married the then Archduke Charles of Austria in 1911.
Charles became heir presumptive to the Emperor Franz Joseph
I of Austria in 1914 after the assassination of his uncle Archduke Franz Ferdinand of Austria, and acceded to the throne in 1916 after the old emperor's death.
After the end of World War I in 1918, the Habsburgs were deposed and the empire became four independent countries, Austria, Hungary, and the newly formed Czechoslovakia and State of Slovenes, Croats and Serbs.
Charles and Zita left for exile in Switzerland and were subsequently removed from Hungary by the Allies to Madeira, where Charles died in 1922.
After her husband's death, Zita and her son Otto served as symbols of unity for the exiled dynasty.
A devout Catholic, she raised a large family after being widowed at the age of 29, and never remarried.
Princess Laetitia Maria of Belgium, Archduchess of Austria-Este
Princess Laetitia Maria of Belgium, Archduchess of Austria- Este(" Laetitia Maria Nora Anna Joachim Zita"; born 23 April 2003) is the third daughter and youngest child of Lorenz, Archduke of Austria- Este and Princess Astrid of Belgium.
She was born at the Saint Jean Hospital in Brussels, Belgium, and is currently 11th in line to the Belgian throne.
Archduke Ferdinand Karl Viktor of Austria-Este
Ferdinand Karl Viktor( 20 July 1821 – 15 December 1849) was Archduke of Austria- Este and Prince of Modena.
Prince Lorenz of Belgium, Archduke of Austria-Este
Prince Lorenz of Belgium, Archduke of Austria- Este( born 16 December 1955) is a member of the Belgian royal family by his marriage with Princess Astrid of Belgium.
Since 1996 he is also head of the House of Austria- Este, a cadet branch of the former Imperial Austrian House of Habsburg- Lorraine.

Answer: Robert I