His father, Thomas O'Leary, arrived on the third boat into Moreton Bay as second mate to the vessel, marrying Mary Mangan, one of the passengers, taking up a farming block on the Logan River trying to grow arrowroot, then becoming a teamster taking many trips to the Gympie goldfields, before moving to Brisbane where, in 1858, second son Michael O'Leary was born in Springhill. Michael O'Leary's siblings were John Joseph (1954-1933), Margret (1862-1944), Thomas Mangan (1865-1897), Mary (born 1868), and Brigid (born 1871).
