James Sinclair was born at Barrogill Castle (Castle of Mey) on 31 May 1766. He was the son of Sir John Sinclair of Mey, Baronet who he succeeded in the baronetcy in 1774. He succeeded as 12th earl of Caithness in 1789, as nearest lawful male heir of William Sinclair, 2nd Earl of Caithness. His claim to the peerage was sustained by the House of Lords.
- John Sinclair, Lord Berriedale who died in 1802 aged 14.
- Alexander Sinclair, 13th Earl of Caithness.
- Four other sons and three daughters.
|Peerage of Scotland|
| Earl of Caithness
|Baronetage of Nova Scotia|
Alexander Sinclair, 13th Earl of Caithness