William Henry “Harry” Cathro was born at Balmain, New South Wales, on 22 December 1894 to parents William Cathro and Amelia Jane Cathro (née McKay). He was the elder of two sons.
Cathro married Isabella Paterson Deas at Petersham, New South Wales, on 27 May 1916 and the couple had a daughter, born in 1917. Cathro was a joiner and cabinetmaker by trade and had been apprenticed to the firm of Alexander & McDowel for five years prior to his enlistment.
Cathro enlisted in the Australian Imperial Force at Sydney on 13 May 1916 and was attached to the 13th Reinforcements for the 30th Battalion. He embarked from Sydney on the troopship Anchises on 24 January 1917. On the voyage, Cathro participated in a concert held on 10 February 1917 singing, “The boys of the old brigade”.
Cathro disembarked at Devonport, England, on 27 March 1917 and marched in to No. 3 Command Depot, Hurdcott, on the Salisbury Plain as part of the 8th Training Battalion. In September 1917, Cathro was still attached to the 8th Training Battalion and was appointed acting sergeant. On 19 September he was sent to the Signalling School at Dunstable, and by December 1917 had qualified as an assistant instructor of signalling. Cathro was promoted to ER corporal on 29 December 1917 and taken on strength in the permanent cadre of the 3rd Training Brigade, based at Codford. On 1 October 1918, Cathro reverted to the rank of private and transferred from the 3rd Training Brigade to the 30th Battalion.
Cathro remained in England until he embarked from London for Australia aboard the troopship Kashmir on 12 March 1919. He was discharged on 1 June 1919.
Following his discharge, Cathro worked as a carpenter, living in the same address in Punchbowl until his death. The couple had twin daughters born in 1917, daughters born in 1920 and 1922, and sons born in 1923 and 1941.
William Henry “Harry” Cathro died at Sydney on 23 December 1972 at the age of 78. Isabella Cathro died at St Leonards, New South Wales, on 26 June 1976 at the age of 79.