Son of Sir William Douglas (d. 1733), 2nd Bart of Kelhead, and Helen Erskine (d. 1754), a half-sister of Boswell's mother Euphemia. Brother of John and William Douglas. Married to a Mrs Young.
Douglas died without issue in 1770 and was succeeded by his nephew, William, 4th Baronet of Kelhead.
Boswell met Douglas at Kelhead on October 6, 1762, describing him as having "been twenty-five years abroad in the East Indies and has made a fortune of £20,000, a fine, hearty man of no great reach but much kindness of heart and a good deal of humour. He was very fond to see me, and as he has a house in London and is to be there next winter, he may be very obliging to me."
There are, however, no records of the two meeting in London during Boswell's famous 1762-63 stay in that city.