Gerald John Koster was born to Erlin and Helen (Schaefer) Koster on January 16, 1925 in Toledo, Ohio. He served in the U.S. Navy during World War II from January 15, 1943 to February 20, 1946.

He was married to Luella Mae Groves and had one son, Gerald Richard Koster.

Gerald died on March 22, 1983 in Perrysburg, Ohio at the age of 58.