James, 3rd Marquess of Thomond, 7th Earl and 12th Baron of Inchiquin, succeeded his brother William to these Irish titles following the latter's death 21 August 1846. James married firstly on 25 November 1800 to Eliza Bridgeman (d. 14 February 1802; secondly to Jane Ottley (d. 8 September 1843); and thirdly on 5 January 1847 to Anne Flint (d. 22 October 1874). James died without heirs on 3 July 1855, at which time the Marquessate of Thomond and the Earldom of Inchiquin became extinct.