He was the son of Donough O'Brien, 3rd Earl of Thomond and Lady Elizabeth FitzGerald. He married Mary Brereton, daughter of William Brereton, 1st Baron Brereton of Leighlin and Margaret Savage, on 13 July 1608 at Brereton, Cheshire, England. He died before 22 April 1639. He was educated at Eton College, Windsor, Berkshire, England. He was invested as a Privy Counsellor (P.C.) [Ireland]. He was educated at Brasenose College, Oxford University, Oxford, Oxfordshire, England. He succeeded to the title of 4th Baron of Ibracken on 31 March 1613, in his father's lifetime. He succeeded to the title of 4th Earl of Thomond [I., 1552] on 5 September 1624.
| Types | Person, Public Official |