He was the son of Sir John Forbes, 7th Baronet, and succeeded his father to the baronetcy on his death in February 1846, at the age of seven.
He was educated at Eton and then joined the Coldstream Guards in 1854; he served in the Crimean War, rising to the rank of captain.
The eldest, John commanded a battalion of the Black Watch at the Battle of Loos.
The second son, Douglas, a Major in the Seaforth Highlanders, was killed on the North-West Frontier of India in 1908.
Gordon Highlanders, was killed by a sniper on 2 June 1915, aged 45, near Festubert whilst working with his men repairing a gap blown in the parapet of their trench.