A boy of twelve when his father died, Carnegie was brought up under the guardianship of his mother and a number of trustees, including Sir Alexander Ramsay Irvine, who completed the legal and financial business connected with the purchase of the Southesk forfeited estates, sold Pittarrow to his uncle George, a returned Jacobite, and by further land transactions paid off the entire debt.
Ambitious from boyhood of ‘restoring his family’, he bought up former Southesk properties, selling some at a high profit,
Active in Forfar and Kincardineshire affairs, and determined to increase his family prestige by entering Parliament, he unsuccessfully opposed Adam Drummond in Aberdeen Burghs in 1780 when Robinson counted both candidates ‘friends’. ‘A very pretty young man’, according to Boswell, he was on friendly terms with Sir Lawrence Dundas, Lord Eglintoun, and other opponents of Henry Dundas.
Carnegie died 25 May 1805.
