Daniel Seymour Katz, professionally known as Dan Seymour, embarked on his educational journey at Senn High School in Chicago, where he laid the foundation for his future endeavors. His academic trajectory took him to the University of Chicago, where he earned a Bachelor of Science degree in Fine Arts. Concurrently, he honed his acting skills by participating in numerous school plays and utilized his evenings to work as an emcee at various Chicago nightclubs, quickly gaining recognition for his exceptional hosting abilities.
Following his time in Chicago, Seymour made the transition to Hollywood, where his robust physique and rugged features rendered him an ideal candidate for playing heavy roles. He opted to change his name, adopting a stage persona that would become synonymous with his on-screen presence. In 1949, Seymour tied the knot with Evelyn Schwartz, with whom he would go on to have two children: Jeff, born in 1950, and Greg, born in 1954.