Daniel Seymour Katz (Dan Seymour's original name) attended Senn High School in Chicago and graduated from the University of Chicago with a B.S. in Fine Arts. While in college, he worked in many school plays and also worked at night as an emcee at various Chicago nightclubs becoming quite successful. He moved to Hollywood, where his rotund build (265 pounds), and swarthy looks made him perfect for a Hollywood heavy, and changed his name. He wed Evelyn Schwartz in 1949. The couple had two children: Jeff (born 1950) and Greg (born 1954).