When Thaddeus Forrest Trego was born on 30 October 1909, in Blackfoot, Bingham, Idaho, United States, his father, Forrest Franklin Trego, was 32 and his mother, Edith Pearl Ewing, was 26. He married Della Smith in 1937. He lived in Riverside, Bingham, Idaho, United States in 1910 and Groveland, Bingham, Idaho, United States in 1930. He died on 17 January 1981, in Blackfoot, Bingham, Idaho, United States, at the age of 71, and was buried in Groveland Cemetery, Blackfoot, Bingham, Idaho, United States.