 Thomas was their only legitimate heir and became the new Earl of Strathmore and Kinghorne on 3 July 1820.On 25 March 1800, Thomas married firstly Mary Elizabeth Louisa Rodney Carpenter (1 January 1783 – 1 June 1811), daughter of George Carpenter (21 October 1713 – 10 November 1782) and his wife Mary Elizabeth Walsh (bap.18 May 1758, d. 27 November 1812).