Marlin and his brother Mike McKeever were the first twins to earn All-America status. They grew up in Los Angeles. Both he and his brother appeared in the 1962 Three Stooges comedy film "The Three Stooges Meet Hercules" playing the Siamese Cyclops twins Ajax and Argo. Marlin appeared with several of his Los Angeles Rams teammates as football players in the 1965 "Perry Mason" episode, "The Case of the 12th Wildcat." Mike died in 1967, after a car accident that left him in a coma for 22 months. On August 18, 1966, Marlin was a passenger in Roman Gabriel's car and lost a finger when Gabriel crashed into a parked car.