James O'Neil Mayne was born into the prominent Mayne family on 21 January 1861. He was the youngest of five children of Patrick Mayne, a butcher and businessman, and his wife Mary McIntosh. Born and raised in Brisbane, James attended Brisbane Grammar School, earned a Bachelor of Arts at the University of Sydney in 1884, then studied medicine at University College Hospital in London. After obtaining his diploma he returned to Australia to work as a resident medical officer at Brisbane General Hospital (now the Royal Brisbane and Women's Hospital) from 1891 to 1898. In 1898 he was appointed medical superintendent, a position he held until his retirement in 1904. A man of substantial independent means thanks to generational wealth, James financed the purchase of the hospital's first x-ray machine and operating theatre equipment, and donated his salary to the hospital's buildings and grounds committee.

James and his older sister, Mary Emilia Mayne, became renowned philanthropists. Neither married. They were among the first and most significant benefactors of The University of Queensland, donating 280 hectares of farmland at Pinjarra Hills for agricultural education in 1923. In 1926, they contributed £63,000 to acquire over 81 hectares at St Lucia, enabling the University's relocation to its current site.

James died on 31 January 1939 at Moorlands, the family home in Auchenflower, Brisbane. James's estate was valued at £113,334 for probate. The primary assets he shared with his sister, who died a year later, included the Brisbane Arcade, Moorlands, and the Regent building. James and Emilia had identical wills, ensuring their estates would be used to support The University of Queensland Medical School in perpetuity.

Mary Emelia Mayne was born into the prominent Mayne family on 31 December 1858. She was the second-youngest of five children of Patrick Mayne, a butcher and businessman, and his wife Mary McIntosh. Born and raised in Brisbane, Mary attended All Hallows' Convent School until 1877. A woman of substantial independent means thanks to generational wealth, she became a mistress of Moorlands, the family home in Auchenflower, hosting many functions.

Mary and her younger brother, James O'Neil Mayne, became renowned philanthropists. Neither married. They were among the first and most significant benefactors of The University of Queensland, donating 280 hectares of farmland at Pinjarra Hills for agricultural education in 1923. In 1926, they contributed £63,000 to acquire over 81 hectares at St Lucia, enabling the University's relocation to its current site.

Mary died on 12 August 1940. Mary's estate was valued at £83,375 for probate. The primary assets she shared with her brother, who died a year earlier, included the Brisbane Arcade, Moorlands, and the Regent building. James and Emilia had identical wills, ensuring their estates would be used to support The University of Queensland Medical School in perpetuity.

Patrick Mayne (ca. 1823-1865) was an Irish-born butcher, businessman and alderman. After migrating to Australia in 1841, he established a successful butchery and expanded into property and finance. On 9 April 1849, he married Mary McIntosh (ca. 1826-1889), who had migrated from Ireland to Australia in 1842. The couple had five children, including Mary Emilia Mayne (1858-1940) and James O'Neil Mayne (1861-1939).

Patrick Mayne died on 17 August 1865 in Brisbane, leaving a substantial estate. His wife, Mary, took over the family business, effectively managing their assets and expanding their landholdings, including acquiring Moorlands at Auchenflower as the family home. She died on 4 September 1889.

None of the Mayne children married. James O'Neil Mayne studied medicine and worked as a resident medical officer, later becoming medical superintendent at Brisbane General Hospital. He and his older sister, Mary Emilia Mayne, became renowned philanthropists. They were among the first and most significant benefactors of The University of Queensland, donating 280 hectares of farmland at Pinjarra Hills for agricultural education in 1923. In 1926, they contributed £63,000 to acquire over 81 hectares at St Lucia, enabling the University's relocation to its current site.

James died in 1939, and Mary in 1940. James's estate was valued at £113,334 for probate, and Mary's at £83,375. Their primary assets included the Brisbane Arcade, Moorlands, and the Regent building. Both had identical wills, ensuring their estates would be used to support The University of Queensland Medical School in perpetuity.