She was the daughter of Captain Andrew Douglas of Mains, Dunbartonshire,[2] and the wife of Sir John Kennedy, 2nd Bt of Culzean, Ayrshire.
Lady Kennedy gave birth to twenty children, but fourteen of them died at a young age.
On 29 February 1760, the Court of Session found the right to the estates to be his, and the House of Lords awarded him the title on 27 January 1762.
Following the death of David Kennedy in 1792, the baronetcy became extinct but the earldom passed to a distant relative.
The earl's mother is said to have moved out of Culzean Castle in 1753 because she disapproved of his plans to improve the house and estate.