[1] John was the eldest son of William Sinclair, 10th Earl of Caithness who died in 1779.
[2] John Sinclair, 11th Earl of Caithness entered the army as an ensign in the 17th Regiment of Foot in September 1772.
[3] He served for some time in America where he was wounded in the groin by a musket ball while reconnoitering with Sir Henry Clinton at the Siege of Charleston.
[3] Sinclair succeeded his father as earl in 1779 and he held the rank of lieutenant-colonel in February 1783.
[3] He had committed suicide by shooting himself and was buried at St Marylebone Parish Church, City of Westminster, London.