Ronald Edmond Thompson was born at the Royal Women's Hospital in Melbourne's inner suburb of Carlton, to John Ronald Ryan and Cecilia Thompson (née Young). Cecilia already had a son with her first husband George Harry Thompson and was living with John Ryan. Cecilia and George had separated in 1915 when George left to fight in the Great War. The relationship never resumed. Cecilia met John Ryan while working as a nurse in Woods Point where he was suffering from lung disease. They formed a relationship in 1924 and later married in 1929, after Thompson's death in 1927 by falling from a tram and getting hit by a car. Ronald then adopted the name Ronald Edmond Ryan. In 1936, Ryan was confirmed in the Roman Catholic Church. He took as his confirmation name Joseph, becoming Ronald Edmond Joseph Ryan. He did not like Edmond and from then on used "Ronald Joseph Ryan".