Tunnell was born in Bryn Mawr, Pennsylvania, though sources conflict as to his year of birth. His tombstone as well as the Social Security Death Index and Tunnell's Department of Veterans Affairs BIRLS Death File reflect a birth date of March 29, 1924. Official NFL records and multiple sources in the early 1960s reported his date of birth as March 29, 1922. Tunnell listed his birth date as March 29, 1923, on his 1942 draft card and on his 1950 application for World War II benefits. Other sources record his birth year as 1925. In 1961, Tunnell joked about his age: "I'm not really 41, as everyone says. I'm closer to 42."