question: Who is Prince Leopold, Duke Of Brabant's maternal grandfather?
context: Title: Prince Leopold, Duke of Brabant
  Passage: Prince Leopold of Belgium, Duke of Brabant, Count of Hainaut( 12 June 1859 – 22 January 1869), was the second child and only son of King Leopold II of Belgium and his wife, Marie Henriette of Austria, and heir apparent to the Belgian throne.
  Title: Marie Henriette of Austria
  Passage: 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.
answer: Archduke Joseph, Palatine of Hungary
citations: Prince Leopold, Duke of Brabant Marie Henriette of Austria