Stair was the son of Sir John Dalrymple, 4th Baronet, and Elizabeth, daughter of Thomas Hamilton-Makgill[1] and heiress and representative of the Viscounts of Oxfuird (or Oxenfoord).
[2] In 1810 he succeeded in the baronetcy, and inherited Oxenfoord Castle, on the death of his father.
However, in 1841 he was created Baron Oxenfoord, of Cousland in the County of Edinburgh, in the Peerage of the United Kingdom, which gave him a seat in the upper chamber of parliament.
He married firstly Harriet, daughter of Reverend Robert Augustus Johnson, in 1795.
Lord Stair died in January 1853, aged 81, and was succeeded in his titles (in the barony of Oxenfoord according to the special remainder) by his younger brother, North Dalrymple.