Born in Paris on 25 August 1820, the son of Admiral Sir John Gordon Sinclair, 8th Baronet (1790–1863), the grandson of Admiral Hon.
Michael de Courcy, and the great-grandson of John de Courcy, 18th Lord Kingsale, Sir Robert Sinclair, 9th Baronet was educated at Bedford School.
He was the ninth of the Sinclair-Lockhart baronets of Murkle in the County of Caithness and of Stevenson in the County of Haddington, created on 18 June 1636 for Sir John Sinclair, 1st Baronet (d. 1649).
[1][2] Sir Robert Sinclair, 9th Baronet died without issue in Haddington, East Lothian on 5 May 1899, aged 78, and was succeeded by his kinsman Major General Sir Graeme Alexander Sinclair-Lockhart, 10th Baronet (1820–1904).
[3] He is buried just in front of the altar inside St Mary's Collegiate Church, Haddington.