According to his attestation papers, dated February 9, 1916 at Mimico, John Oliver Thornborough was born on January 7, 1875 in Worchester, England. He listed his wife Emma Thornborough, Heman Street, Mimico as his next of kin. He indicated that he was a Contractor and that he had had previous military experience with the 12th Regiment York Rangers. He was 40 years and 1 month of age and stood 5 feet 8 inches tall. He had brown eyes, dark brown hair and a dark complexion.
According to the 1912 and 1921 Toronto City directories he lived on the south side of Heman Street, Mimico.