Friedlaender was born in Berlin as the son of Carl Friedlaender (1817–1876), a professor of economics. His grandfather was Nathan Friedlaender (died 1830), a Berlin physician and university lecturer. Among his siblings was Immanuel Friedlaender (1871–1948), a distinguished volcanologist. He studied mathematics, physics, botany, and physiology in Berlin, earning a Ph.D. in zoology in 1888. As a well-to-do donor, he supported the anarchist journal Kampf and published in the journal Der Sozialist. He gave substantial financial support to Magnus Hirschfeld 's Scientific-Humanitarian Committee (Wissenschaftlich-humanitäres Komitee, or WhK) in Berlin. The primary goal of the WhK was to work against Paragraph 175 of the Imperial Penal Code, which criminalized "unnatural vice" between males. The WhK assisted defendants in criminal trials, conducted public lectures, and gathered signatures on a petition for the repeal of the law. It found some parliamentary support for its law reform efforts in the Social Democratic Party.