The son of John Stephen Mulcahy (1852-1932),Deaths: Mulcahy, The Argus, (Tuesday, 29 March 1932), p.1. and Margaret Jane Mulcahy (1856-1930), née Roberts,Deaths: Mulcahy, The Argus, (Monday, 7 July 1930), p1. John George Mulcahy was born on 12 August 1876.
