Elisabeth of Sicily, Duchess of Bavaria
Elisabeth of Sicily (1310–1349) was a daughter of Frederick III of Sicily and Eleanor of Anjou.
Her siblings included: Peter II of Sicily and Manfred of Athens.
After her death her title was given to Georgia Lanza.
On June 27, 1328, Elisabeth married Stephen II, Duke of Bavaria, son of Louis IV, Holy Roman Emperor and Beatrix of Silesia-Glogau.
The couple had three sons and a daughter, they were:
Princess Elisabeth Marie of Bavaria
Princess Elisabeth of Bavaria (8 January 1874 – 4 March 1957) was a member of the Bavarian Royal House of Wittelsbach.
She was known as Princess of Bavaria until 1918.
Duchess Maria Anna Josepha of Bavaria
Maria Anna Josepha of Bavaria(" Maria Anna Josepha Augusta"; 7 August 1734 – 7 May 1776) was a Duchess of Bavaria by birth and Margravine of Baden- Baden by marriage.
She was nicknamed the" savior of Bavaria".
She is also known as" Maria Josepha" and is sometimes styled as a" princess of Bavaria".
Beatrice of Sicily (1326–1365)
Beatrice of Sicily (5 September 1326 – 12 October 1365) was a daughter of Peter II of Sicily and his wife Elisabeth of Carinthia.
She was born into the House of Aragon.
Duke Pius August in Bavaria
Duke" Pius August" in Bavaria, full German name:" Pius August Herzog in Bayern"( born 1 August 1786 in Landshut, Electorate of Bavaria; died 3 August 1837 in Bayreuth, Kingdom of Bavaria) was a Duke in Bavaria as a member of the Palatine Birkenfeld- Gelnhausen line of the House of Wittelsbach.
Pius
August was a grandfather of Empress Elisabeth of Austria through his son Duke Maximilian Joseph in Bavaria, as well as a great grandfather of Queen Elisabeth of the Belgians and an ancestor of the current generations of the Belgian and Italian Royal Families and the Grand Ducal Family of Luxembourg.
Elisabeth of Lorraine
Elisabeth of Lorraine (9 October 1574 – 4 January 1635), was a Duchess and an Electress consort of Bavaria by marriage to Maximilian I, Elector of Bavaria.
Princess Maria Elisabeth of Bavaria
Princess Maria Elisabeth of Bavaria( 9 September 1914 – 13 May 2011) was the eldest daughter of Prince Franz of Bavaria, third son of Ludwig III of Bavaria.
Elisabeth of the Palatinate
Elisabeth of the Palatinate( 26 December 1618 – 11 February 1680), also known as Elisabeth of Bohemia, Princess Elisabeth of the Palatinate, or Princess- Abbess of Herford Abbey, was the eldest daughter of Frederick V, Elector Palatine( who was briefly King of Bohemia), and Elizabeth Stuart.
Elisabeth of the Palatinate is a philosopher best known for her correspondence with René Descartes.
She was critical of Descartes' dualistic metaphysics and her work anticipated the metaphysical concerns of later philosophers.
Duke Maximilian Emanuel in Bavaria
Duke Maximilian Emanuel in Bavaria, full German name:" Maximilian Emanuel, Herzog in Bayern"( 7 December 1849 in Munich, Kingdom of Bavaria – 12 June 1893 in Feldafing, Kingdom of Bavaria) was a Duke in Bavaria and member of the House of Wittelsbach.
Maximilian Emanuel was the tenth and youngest child of Duke Maximilian Joseph in Bavaria and his wife Princess Ludovika of Bavaria.
Maximilian Emanuel was the brother of Elisabeth of Bavaria, Empress of Austria and Queen of Hungary.
Frederick III of Sicily
Frederick II (or III) (13 December 1272 – 25 June 1337) was the regent (from 1291) and subsequent King of Sicily from 1295 until his death.
He was the third son of Peter III of Aragon and served in the War of the Sicilian Vespers on behalf of his father and brothers, Alfonso ΙΙΙ and James ΙΙ.
He was confirmed as King of Trinacria (another name for the island of Sicily) by the Peace of Caltabellotta in 1302.
His reign saw important constitutional reforms: the "Constitutiones regalesCapitula alia", and "Ordinationes generales".

Question: Who is the paternal grandfather of Elisabeth Of Sicily, Duchess Of Bavaria?
Answer: Peter III of Aragon