Question: Who is the grandfather of James Mayer de Rothschild?

Knowledge 1: James Mayer de Rothschild
James Mayer de Rothschild, Baron de Rothschild (15 May 1792 – 15 November 1868), born Jakob Mayer Rothschild, was a German-French banker and the founder of the French branch of the Rothschild family. [SEP] Knowledge 2: Nicole Stéphane
The elder of the two daughters of Baron James-Henri de Rothschild and his first wife, Claude Dupont, Nicole Stéphane was a member of the Rothschild banking family of France. Her immediate family, however, also was deeply immersed in the arts. Her paternal grandfather, Baron Henri de Rothschild, was a playwright and theatrical producer who wrote under the names Charles des Fontaines and André Pascal and owned Théâtre Antoine and Théâtre Pigalle. Her first cousin Philippine de Rothschild was an actress with the Comédie-Française, using the name Philippine Pascal. And her father's brother, the vintner Philippe de Rothschild, wrote plays, owned theatres and produced films.
Knowledge 1: Rothschild banking family of France
The Rothschild banking family of France is a French banking dynasty founded in 1812 in Paris by James Mayer de Rothschild (1792–1868). James was sent there from his home in Frankfurt, Germany, by his father, Mayer Amschel Rothschild (1744–1812). Wanting his sons to succeed on their own and to expand the family business across Europe, Mayer Amschel Rothschild had his eldest son remain in Frankfurt, while his four other sons were sent to different European cities to establish a financial institution to invest in business and provide banking services. Endogamy within the family was an essential part of the Rothschild strategy in order to ensure control of their wealth remained in family hands. [SEP] Knowledge 2: Nicole Stéphane
The elder of the two daughters of Baron James-Henri de Rothschild and his first wife, Claude Dupont, Nicole Stéphane was a member of the Rothschild banking family of France. Her immediate family, however, also was deeply immersed in the arts. Her paternal grandfather, Baron Henri de Rothschild, was a playwright and theatrical producer who wrote under the names Charles des Fontaines and André Pascal and owned Théâtre Antoine and Théâtre Pigalle. Her first cousin Philippine de Rothschild was an actress with the Comédie-Française, using the name Philippine Pascal. And her father's brother, the vintner Philippe de Rothschild, wrote plays, owned theatres and produced films.
Knowledge 1: James Mayer de Rothschild
James Mayer de Rothschild, Baron de Rothschild (15 May 1792 – 15 November 1868), born Jakob Mayer Rothschild, was a German-French banker and the founder of the French branch of the Rothschild family. [SEP] Knowledge 2: Rothschild family
The second French branch was founded by Nathaniel de Rothschild (1812–1870). Born in London, he was the fourth child of the founder of the British branch of the family, Nathan Mayer Rothschild (1777–1836). In 1850 Nathaniel Rothschild moved to Paris to work with his uncle James Mayer Rothschild. In 1853 Nathaniel acquired Château Brane Mouton, a vineyard in Pauillac in the Gironde département.  Nathaniel Rothschild renamed the estate Château Mouton Rothschild, and it would become one of the best known labels in the world. In 1868, Nathaniel's uncle, James Mayer de Rothschild, acquired the neighbouring Château Lafite vineyard.

Answer: Amschel Moses Rothschild