Gilbert Kennedy, 3rd Earl of Cassilis
The son of Gilbert Kennedy, 2nd Earl of Cassilis, he succeeded to the titles of 5th Lord Kennedy and 3rd Earl of Cassillis in August 1527. On 6 February 1540/41 he had a charter of the Fief of Cassilis.
In November, 1542, Kennedy, in his late twenties at the time, was taken prisoner at the Battle of Solway Moss, and after a short stint in the Tower of London, was placed under the care of Thomas Cranmer, Archbishop of Canterbury. Scottish historian Gilbert Burnet (1643-1715) believed that it was this relationship with Cranmer that led Kennedy toward Protestantism, as certainly he was one of the first of the Scottish nobility to adopt Reformed views. However, since his time with Cranmer lasted only one month, it is likely that his earlier contact with Buchanan had been a stronger influence in this regard.
Sir Thomas Wharton, Warden of the English West March, wrote to the Privy Council of King Henry VIII, on the tenth of December 1542, regarding ransoms for prisoners taken at the battle, including the Earl of Cassilis, who was taken by Batill Routlege. Credit was also given to John Musgrave who "claimeth a part for the loan of his horse to the said Routlege." 
In 1558 he was present, as one of the eight Commissioners appointed by the Scottish Parliament, at the marriage of Mary, Queen of Scots, to the Dauphin of France, to whom the Scottish deputies unanimously refused the Crown matrimonial. The Court of France appeared deeply mortified by this disappointment, and the Earl of Cassilis, with two others of the Commissioners, dying in one night, on 28 November 1558, at Dieppe, a report was raised that they had been poisoned, which was further countenanced by the death of a fourth Commissioner, Lord Fleming, at Paris, on 16 December 1558. However, according to the Dictionary of National Biography, this report was untrue, as the actual dates of death of these persons were not the same, Cassilis dying in November.
The Earl married Margaret Wallace in 1540 and they had four children.
- Katherine Kennedy
- Gilbert Kennedy, 4th Earl of Cassilis (c. 1541–1576)
- Sir Thomas Kennedy, Master of Cassilis (b. between 1543–1558, d. 1602)
- Lady Janet Kennedy Stewart, (bef. 1558–c.1598), married Robert Stewart, 1st Earl of Orkney
- Lady Isobel Kennedy b. 24 July 1542 d. 12 Jan 1598 married Sir Patrick Mc Elwain of Thomaston Castle and had descendants
- Groome, Francis, Hindes, ed. (1885–1900). Dictionary of National Biography. London: Smith & Elder. p. 30:418. Retrieved 26 May 2017.
- MacCulloch, Diarmaid (1996). Thomas Cranmer: A Life. New Haven: Yale UP. p. 295-96. ISBN 9780300074482. Retrieved 26 May 2017.
- Nicolson, Joseph. The History and Antiquities of the Counties of Westmorland and Cumberland (W Strahan, London 1777) https://archive.org/details/historyandantiq00burngoog.
- Dictionary of National Biography. Smith, Elder, & Co. 1885–1900. p. 419. Retrieved 7 August 2016.
- Historic account of the family of Kennedy, Ailsa, Cassilis, (1849), appendix, pp.1-6
|Peerage of Scotland|
|Earl of Cassilis