O'Leary's brothers John Justin O'Leary (born Peterborough 31 July 1892 – 14 February 1918), and (Humphrey) Emmet O'Leary (born Georgetown 6 May 1886 – 9 March 1918) both enlisted with the First AIF, both killed in action. Their mother, Susan O'Leary, was listed as next of kin. She later became Sue Holland.
