Alexandre Louis Philippe Marie Berthier, 4th Prince of Wagram
Alexandre Louis Philippe Marie Berthier( July 20, 1883, Paris – May 30, 1918, Barenton- sur- Serre; 4th Prince de Wagram) was the son of Bertha Clara von Rothschild of the German branch of the prominent Rothschild family and Louis Philippe Marie Alexandre Berthier, 3rd Prince de Wagram( 1836 – 1911).
The family resided in the ancestral home, the Château de Grosbois, a large estate in Boissy- Saint- Léger, southeast of Paris.
Alexandre Berthier was an active collector of impressionist paintings and owned works by Gustave Courbet, Édouard Manet, Claude Monet, and Pierre- Auguste Renoir.
Through a relationship with Marie- Louise Salivas dite Welson, he had a daughter, Monique Berthier de Wagram( 1914–2000).
Alexandre Berthier had not yet married when he was killed in action at Barenton- sur- Cere during World War I.
As such, the title became extinct.
His daughter, though married three times( to two men), had no children, and so Alexander Berthier has no living descendants.
Prince Philippe, Count of Paris
Prince Philippe of Orléans, Count of Paris( Louis Philippe Albert; 24 August 1838 – 8 September 1894), was the grandson of Louis Philippe I, King of the French.
He was the Count of Paris as Orléanist claimant to the French throne from 1848 until his death.
Duchess Maria Elisabeth in Bavaria
Duchess" Maria Elisabeth" Amalie Franziska in Bavaria( 5 May 1784 – 1 June 1849) was a Duchess in Bavaria as a member of the Palatine Birkenfeld- Gelnhausen line of the House of Wittelsbach and through her marriage to Louis- Alexandre Berthier became Princess of Wagram and Princess of Neuchâtel.
Napoléon Alexandre Berthier, 2nd Prince of Wagram
Napoléon Alexandre Louis Joseph Berthier, 2nd Prince of Wagram (11 September 1810, Paris10 February 1887, Paris) was a French politician and nobleman.
Son of Louis-Alexandre Berthier, 1st Prince of Wagram, and Duchess Maria Elisabeth in Bavaria (and by his mother, grandnephew of King Maximilian I of Bavaria).
George Louis, Prince of Erbach-Schönberg
George Louis, Prince of Erbach- Schönberg( 1 January 190327 January 1971) was the 3rd Prince of Erbach- Schönberg, elder son of Alexander, 2nd Prince of Erbach- Schönberg.
Louis-Alexandre Berthier
Louis- Alexandre Berthier( 20 November 1753 – 1 June 1815), 1st Prince of Wagram, Sovereign Prince of Neuchâtel, was a French Marshal and Vice- Constable of the Empire, and Chief of Staff under Napoleon.
Louis Philippe, Crown Prince of Belgium
Louis- Philippe, Crown Prince of Belgium( Louis Philippe Léopold Victor Ernest; 24 July 1833 – 16 May 1834), was the eldest child and heir- apparent of King Leopold I of the Belgians and his second wife, Princess Louise d'Orléans.
Louis d'Orléans, Prince of Condé
"Louis" Philippe Marie Léopold d'Orléans (15 November 1845 – 24 May 1866) was a member of the House of Orléans and held the title of Prince of Condé.
He was the first member of a royal house to visit the Australian continent.
Jean-Marie Alexandre
Jean-Marie Alexandre is a French politician, who, from 1987 until 1994, was a Member of the European Parliament representing France for the Socialist Party.
Alexandre Berthier, 3rd Prince of Wagram
Louis Philippe Marie "Alexandre" Berthier, 3rd Prince of Wagram (24 March 1836, Paris – 15 July 1911, Château de Grosbois) was a French nobleman and prince of Wagram.
He was the son of Napoléon Alexandre Berthier and Zénaïde Françoise Clary and grandson of Louis Alexandre Berthier.

Question: Who is the paternal grandfather of Alexandre Berthier, 3Rd Prince Of Wagram?
Answer: Louis-Alexandre Berthier