Kerr, a professional soldier, who served under Marlborough and was wounded at Sheriffmuir, was the brother of the Duke of Roxburghe, the head of the Squadrone, secretary of state for Scotland 1716-25. Returned in 1715 for Dysart Burghs on the interest of Lord Rothes, also a Squadrone leader, he voted consistently with the Government. In 1721, his Dysart seat being no longer available, he accepted an invitation to contest Berwick,1Rich. How and others to Kerr, 20 June 1721, Sunderland (Blenheim) mss. which he had represented under Anne, but withdrew to stand for Aberdeen Burghs where he was returned against an Argyll Whig, Colonel John Middleton, who was awarded the seat on petition, though ‘such was the number of friends Kerr personally had that he came within one vote’. Describing the decision as ‘a blow to the Duke of Roxburghe and ... a great victory to the Duke of Argyll’, but of no consequence to the Government, since both candidates were supporters of the ministry, Lord Finch, continued:
When Kerr desired me to help him I knew not the name of his boroughs and when I asked him that he could name me but three out of five, so I was forced to spend 1/- for the list of the Parliament, so that I might know at least that.2To Ld. Nottingham, 29 Oct. 1722, Finch mss.
Returned next year at a by-election for Berwick, he did not stand again, dying 17 Jan. 1741.