Source: 153rd Wellington web site.
Family Search: Gerald Joseph O’Brien was born on 9 September 1900, in Stratford, Perth, Ontario, Canada. He had at least 1 son and 3 daughters with Caroline F Erd. He lived in Fergus, Centre Wellington, Wellington, Ontario, Canada in 1916 and Toledo, Lucas, Ohio, United States in 1940. He registered for military service in 1916. In 1933, at the age of 33, his occupation is listed as street car inspector in Toledo, Lucas, Ohio, United States. He died on 14 December 1977, in Ohio, United States, at the age of 77, and was buried in Calvary Cemetery, Toledo, Lucas, Ohio, United States.
Underage. Note that headstone gives date of birth on September 9, 1900 making him 15 years old when he enlisted.
“Trade listed as Laborer. DOB 9-9-98, born Stratford, Ontario. 5 foot 6 inches. Brown eyes, dark brown hair. Catholic. NOK William Joseph OBrien, father. Josephine OBrien, mother.Enlisted Fergus 3-2-16 (age 17 years 5 months). On 153rd Battalion Nominal Roll 2-4-16, no transfer noted. On 153rd Nominal Rolls as published Guelph Mercury 10-6-16 and 1-12-16. Embarked with 153rd Halifax N.S. SS Olympic 29-4-17. Taken on Strength 18th Battalion 15-12-17. Returned to Canada for Discharge aboard SS Caronia, Halifax N.S. 22-5-19. Demobilized London 24-5-19. Ancestry Family Tree: born 9-9-1900. Married 6-10-25 at Toledo, Ohio to Caroline F. Erd. Ohio Death Records: died 14-12-77 at Toledo, Ohio. U.S. Find a Grave: Buried Calvary Cemetery, Toledo.
File: RG 150, Accession 1992-93/166, Box 7401 – 59, courtesy Library & Archives Canada.”
History of the 18th Battalion CEF, "The Fighting Eighteenth" 