 On 26 March 1564 Knox stirred controversy again, when he married Margaret Stewart, the daughter of an old friend, Andrew Stewart, 2nd Lord Ochiltree, a member of the Stuart family and a distant relative of the Queen, Mary Stuart. The marriage was unusual because he was a widower of fifty, while the bride was only seventeen. Very few details are known of their domestic life. They had three daughters, Martha, Margaret, and Elizabeth.
