A Lexander Campbell, Lord Polwarth, was the third son of Patrick Hume, first Earl of Marchmont. Having married in 1697 the daughter and heiress of Sir George Campbell, of Cessnock, he changed his name after his father-in-law's death and sat in the Court of Session as Lord Cessnock, assuming the title of Polwarth on his elder brother's death in 1709.