Mabel Isabel Stewart was born on 27 Jun 1873, the youngest of six daughters of Robert Frederick Augustus Stewart (1831-1896) and Sarah Smith (1836-1925) who were married on 19 Apr 1856. RFA Stewart was the eldest son of Captain Robert Petty Stewart of the 40th Regiment. He was employed by the Commercial Bank in Launceston. Sarah was the daughter of Archibald and Christiana Smith of 'Selma', Avoca.
On 8 May 1898 in Newcastle, NSW, Mabel married Harold Thomsett, eldest son of Rev. W Thomsett, of Derbyshire, England. Captain Thomsett, of the Berean and the Lanoma, was a master mariner and later a Port Phillip pilot based at Williamstown.
Mabel was an amateur artist. The QVMAG holds the portraits she painted of her parents in 1902. Her eldest child Donald was born in Sydney in 1898, and her son Brian was born at her mother's home at 'Tarnpire' on 5 Jan 1903. There were several other children as well. Harold and Mabel built their home 'Berean' at 89 Esplanade, Williamstown. Mabel could look out from the front windows across Port Phillip Bay and see the shipping lanes where Harold guided vessels to port. Mabel died in Melbourne in 1959 at the age of 68. See The Examiner 6 May 2006, p.35.