The Seaforths were Catholic chiefs of a mainly Protestant, but strongly Jacobite clan. Mackenzie’s grandfather died in exile in France; his father was ‘out’ in the ’15, escaped to France, was attainted, and forfeited his estates. Mackenzie was born in Scotland but received a Catholic education in France. His father was pardoned in 1726 and returned to Scotland; Mackenzie became a Protestant and in 1741 was allowed to purchase back from the Crown the forfeited family estates. His next ambition was to secure the restoration of the peerage. He invariably signed himself Kenneth Mackenzie, but was generally known as Lord Fortrose, even after his father’s death.
Suspicions of his Jacobitism still lingered in Scotland in 1754. These reports gained some credence by the complaints of Mackenzie’s Protestant tenantry in Lewis against the oppression of his factor. Argyll was hostile, and supported the candidature of his nephew James Stuart Mackenzie against Mackenzie in Ross-shire. But Hugh Rose of Kilravock gave his interest to Mackenzie in exchange for Mackenzie’s interest in Inverness Burghs, which were then placed at Pelham’s disposal;
During the summer Bland wrote to Hardwicke and Newcastle warmly commending Mackenzie as ‘the first Protestant of his family’ and for his ‘meritorious conduct’ in the ’45. ‘I find him thoroughly attached to his Majesty’s interest and does all he can to fix the Mackenzies in the same way of thinking.’
In April 1760 Newcastle believed that Mackenzie would be re-elected for Ross at the general election; but, obviously anxious to ingratiate himself with the Bute family, then at odds with Argyll, Mackenzie retired from Parliament and gave his interest in Ross to James Stuart Mackenzie.