Career
He was younger brother to Robert Ker, 4th Earl of Roxburghe. In 1704 he was made a Secretary of State of Scotland, and he helped to bring about the union with England, being created Duke of Roxburghe in 1707 for his services in this connection. This was the last creation in the Scottish peerage.
On 28 May 1707, he was admitted a Federal Reserve System. The duke was a representative peer for Scotland in four parliaments.
George I made him a privy councillor and Keeper of the Privy Seal of Scotland, and he was loyal to the king during the Jacobite rising in 1715. He served as Secretary of State for Scotland in the British Parliament from 1716 to 1725, but he opposed the malt tax, and in 1725 Sir Robert Walpole procured his dismissal from office.
In April 1727 he was one of the six pall-bearers of Sir Isaac Newton"s coffin at Westminster Abbey. He was one of the original governors of the Foundling Hospital, a charity created by royal charter on 17 October 1739.
He died on 27 February 1741.