Of the renowned Arnstein Family of dominant court financiers in Vienna in the 18th and first half of 19th century. The Arnsteins married into other leading Jewish families, such as Gomperz, Itzig, Mendelssohn and Pereira.
Son of Adam Isaac Arnstein. Nathan Adam made large scale loans to the court of Joseph II. Together with his brother in law and partner, Bernhard Eskeles, he expanded the family firm during the Napoleonic Wars. He was among the most famous bankers in Austria and was ennobled in 1795. in 1797 he was title a Baron. He supported Tyrolese peasants in their revolt against the French, and was involved in the Jewish Viennese Community. Along with other notables, he signed a petition to the king requesting rights for the Jews during the Congress of Vienna in 1814-1815). He married Franziska Itzig (Fanny) who led a famous salon. Their daughter Henrietta married Heinrich Pereira , a reputedly relative of Diego d Aguilar.