Gerald was born in 1889 to William Doak and his wife Margaretta Elliot, land owners and farmers from Kinnego House, Lurgan. Sometime before the 1911 census, he moved to Belfast to become a bookkeeper - as the youngest son of a successful farmer, perhaps he was not in line to inherit the farm. In any case, Gerald enlisted in the war effort, joining the Army Service Corps. His brother Howard was serving with the Canadian Army.

Gerald had an exemplary military record and won many awards, inlcuding the Meritorious Service Medal in November 1916 and the Belgian Croix de Guerre in July 1918. He was twice Mentioned in Despatches and was awarded the Divisional Gallantry Certificate.

Four weeks before the end of the war, in October 1918, Gerald married May Davidson Meharg in Castleton Presbyterian Church, the newspaper announcement outlining all of Gerald’s awards. After the war, the couple lived in Glandore Avenue, the home of his new wife's uncle, H.K. Collins, clerk of session at Castleton Presbyterian Church. By 1919, they were living in Castlereagh, where their first child Reginald William Doak was born.

By 1928 Gerald had moved to London, living in Wandsworth, then Balham. In the 1939 Register, his occupation is listed as a Fish Buyer and Supervisor.

Gerald died in St Guy’s Hospital, London in 1960 at the age of 66 years old. He left everything to his son Reginald, now a police inspector.