WordNet sense 1 (United States comedian; one of four brothers who made motion pictures together (1901-1979)):

Zeppo, Herbert Marx

WordNet sense 2 (United States comedian; one of four brothers who made motion pictures together (1893-1964)):

Harpo, Arthur Marx

WordNet sense 3 (United States comedian; one of four brothers who made motion pictures together (1891-1961)):

Leonard Marx

WordNet sense 4 (United States comedian; oldest of four brothers who made motion pictures together (1890-1977)):

Groucho, Julius Marx

WordNet sense 5 (founder of modern communism; wrote the Communist Manifesto with Engels in 1848; wrote Das Kapital in 1867 (1818-1883)):

Karl Marx