[2] His only sister, Lady Jean Ker, was married to Colin Lindsay, 3rd Earl of Balcarres, a prominent supporter of James II of England.
Harry Ker and Lady Margaret Hay (the only daughter of William Hay, 10th Earl of Erroll and Lady Anne Lyon, daughter of Patrick Lyon, 1st Earl of Kinghorne).
[1] On 10 October 1675, Roxburghe was married to Lady Margaret Hay, eldest daughter of John Hay, 1st Marquess of Tweeddale and Lady Jean Scott, the second daughter of Walter Scott, 1st Earl of Buccleuch.
[1] Together, they were the parents of:[1] Roxburghe died on 6 May 1682 when HMS Gloucester ran aground on a sandbank off the Norfolk coast.
When Robert died unmarried 14 years later, the title passed to his second son, John, who was created Lord Ker of Cessford and Cavertoun, Viscount of Broxmouth, Earl of Kelso, Marquess of Bowmont and Cessford, and the 1st Duke of Roxburghe on 25 April 1707.