 The third of five children born to Lucius O'Brien, 15th Baron Inchiquin and Ethel Foster, and younger brother of Donough O'Brien, 16th Baron Inchiquin, he was also the uncle of the current incumbent, Conor O'Brien, 18th Baron Inchiquin.He was educated at Eton College and Magdalen College, Oxford where he graduated MA.He briefly served in Britain in World War I, which ended before he would have gone on active service or been promoted, as a Gunner in the Royal Field Artillery.