His grandfather had added to the family's wealth and estates by marriage to the heiress Mary Widenham of Kildimo.
He was elected in 1799 as Member of Parliament for his father's old seat Kilmallock to the Irish House of Commons, sitting until the union of Ireland and Great Britain in 1800/01.
He was created Baron Adare on 31 July 1800 – as a staunch supporter of the political union, he was recommended by Lord Cornwallis [2] – Viscount Mount-Earl on 3 February 1816, and Earl of Dunraven and Mount-Earl on 5 February 1822, all titles in the Peerage of Ireland.
His earldom lasted only two years until his death in 1824, when his son, Windham Henry Quin, became the 2nd Earl of Dunraven and Mount-Earl.
[3] He married firstly Lady Frances Muriel Fox-Strangways, daughter of Stephen Fox-Strangways, 1st Earl of Ilchester, and his wife, the former Elizabeth Horner, on 24 August 1777.