He was born in Dean House in western Edinburgh on 25 September 1804 the son of Williamina Belches Stuart of Invermay and Sir William Forbes of Monymusk and Pitsligo, 7th baronet.
When his father died in 1828 he became 8th baronet, and took over the family home at 86 George Street.
In 1833 he was elected a Fellow of the Royal Society of Edinburgh his proposer being Thomas Charles Hope.
Due to the lack of male heir the baronetcy passed to his nephew, William Stuart Forbes (1835-1906), son of Charles Hay Forbes, thereafter being titled as 9th baronet.
They had one daughter, Harriet Williamina Hepburn-Forbes (1835-1869),[4] who was the mother of Charles John Robert Hepburn-Stuart-Forbes-Trefusis, 21st Baron Clinton.