He was the second son of Sir John Dalrymple of Cousland, 4th Baronet (d. 1810), a Baron of the Court of the Exchequer of Scotland, and Elizabeth Hamilton-Makgill.

Among his siblings were Henrietta Dundas Dalrymple-Hamilton, who married Augustin-Gustave de Franquetot, 3rd Duke of Coigny.

[1] His paternal grandparents were Sir William Dalrymple of Cranstoun, 3rd Baronet, and the former Agnes Crawford.

[1] On 10 January 1853, upon the death of his elder brother John Hamilton Dalrymple, former MP for Midlothian, he succeeded as the 9th Earl of Stair in the Peerage of Scotland, as well as the 2nd Baron Oxenfoord in the Peerage of the United Kingdom (by special remainder) and the 6th Dalrymple Baronet of Killock in the Baronetage of Nova Scotia.

[3] Together, they were the parents of:[1] Lord Stair died at Oxenfoord Castle on 9 November 1864 and was succeeded by his eldest son from his first marriage, John.