It looks like your Jack Mulvahill maybe John Mulvihill who died 20th September 1914.
The Sydney Morning Herald (NSW : 1842 - 1954) (about) < Saturday 26 September 1914
MULVIHILL - September 20, at Lithgow. Hospital, John, beloved husband of Annie Mulvihill (late ofFix this text Tumut), aged 53 years.
The Sydney Morning Herald (NSW : 1842 - 1954) (about) < Thursday 24 September 1914 >
TELEGRAPH LINESMAN KILLED. LITHGOW. Tuesday. A telegraph linesman on the Rydal-Wallerawang deviation, named John Mulvihill, was admitted to Lithgow Hospital on Sunday suffering from injuries sustained through having been knocked down by a train near Rydal station. He died about five hours after ad mission Deceased was about 55 years of age, and lived at Cootamundra. Ho left a widowFix this text and family.
Could this be his son?
The Sydney Morning Herald (NSW : 1842 - 1954) (about) < Wednesday 28 November 1917 MULVIHILL. - Killed In action in Belgium, October 19, 1917. Private Laurence Rupert, dearly loved son of the late John Mulvihill (Tumut) and Mrs. Mulvi hill (Cowra), and loved brother of Clarice, Edward,Fix this text and Mona.
Possible marriage in NSW 1907 10149/1907MULVIHILLJOHN PMCLARENANNIEBROKEN HILL