Karl Popper was born in Vienna on July 28, 1902, the son of a barrister.
All of Karl Popper's grandparents were Jewish but were not devout, and as part of the cultural assimilation process, the Popper family converted to Lutheranism before Karl was born, and so he received Lutheran baptism. Karl's father Simon Siegmund Carl Popper was a lawyer from Bohemia and a doctor of law at the Vienna University, and mother Jenny Schiff was of Silesian and Hungarian descent. Karl Popper's uncle was the Austrian philosopher Josef Popper-Lynkeus. After establishing themselves in Vienna, the Poppers made a rapid social climb in Viennese society: Simon Siegmund Carl became a partner in the law firm of Vienna's liberal mayor Raimund Grübl and, after Grübl's death in 1898, Simon took over the business. Karl received his middle name after Raimund Grübl. (Popper himself, in his autobiography, erroneously recalls that Grübl's first name was Carl. His father was a bibliophile who had 12, 000–14, 000 volumes in his personal library and took an interest in philosophy, the classics, and social and political issues. Popper inherited both the library and the disposition from him. Later, he would describe the atmosphere of his upbringing as having been "decidedly bookish. "