On his death in 1551, Murrough was succeeded in the earldom, according to the special remainder, by his nephew, the second Earl (see
Earl of Thomond for the later history of this title), but the barony of Inchiquin passed to his son Dermod, the second baron. Dermod's great-great-grandson, the sixth baron, was a prominent military commander during the
Irish Confederate Wars (1643–48), first for the
English Parliament, then as a Royalist commander during the
Cromwellian conquest of Ireland (1649–53) during the
Wars of the Three Kingdoms. In 1654 he was created
Earl of Inchiquin in the Peerage of Ireland. He was succeeded by his son,
William O'Brien, 2nd Earl of Inchiquin, who served as governor of
English Tangier and as
Governor of Jamaica. His son,
William O'Brien, 3rd Earl of Inchiquin, became
Governor of Kinsale in 1693. The fourth earl, also named
William O'Brien, represented
Windsor,
Camelford and
Aylesbury in the
British House of Commons. The fifth earl,
Murrough O'Brien, was the nephew and son-in-law of his predecessor. In 1800, he was created
Marquess of Thomond in the Peerage of Ireland, with remainder to his brother, the Honorable
Edward Dominic O'Brien, a captain in the
British Army. The following year he was made
Baron Thomond of Taplow in the County of Buckingham in the
Peerage of the United Kingdom to allow him to sit in the
House of Lords, with remainder to the male heirs of his body. He died without male issue in 1808, when the barony of Thomond became extinct. He was succeeded in the marquessate according to the special remainder, and in the other Irish titles, by his nephew
William O'Brien, 2nd Marquess of Thomond, the third son of the aforementioned Captain Edward O'Brien. The second marquess was an
Irish representative peer. In 1826 he was created
Baron Tadcaster of Tadcaster in the County of York in the Peerage of the United Kingdom. He had no sons and on his death in 1846 the barony of Tadcaster became extinct. He was succeeded in the Irish peerages by his younger brother,
James O'Brien, 3rd Marquess of Thomond, an
admiral in the
Royal Navy. He had no sons and on his death in 1855 the marquessate and earldom of Inchiquin became extinct. In 1855, he was succeeded in the barony of Inchiquin by his distant relative Sir
Lucius O'Brien, 5th Baronet, who became the 13th Baron Inchiquin. The '''O'Brien Baronetcy''', of Leaghmenagh in the County of Clare, had been created in the
Baronetage of Ireland in 1686 for Donough O'Brien, who had earlier represented
County Clare in the
Irish House of Commons. He was the great-great-grandson and namesake of Donough O'Brien (died 1582), younger son of the first Earl of Thomond and first Baron Inchiquin. His grandson, the second baronet, great-grandson the third baronet, and great-great-grandson the fourth baronet, also represented County Clare in the Irish Parliament, with the fourth baronet also representing
Ennis. The latter was succeeded by his son, the fifth baronet. Before becoming the 13th Baron, the fifth Baronet O'Brien had represented
County Clare in the House of Commons and was later an Irish Representative Peer. He also served as
Lord Lieutenant of County Clare. He was succeeded by his son,
Edward O'Brien, 14th Baron Inchiquin, also an Irish Representative Peer and Lord Lieutenant of County Clare. His son,
Lucius O'Brien, 15th Baron Inchiquin, also sat in the House of Lords as an Irish Representative Peer, and also served in the British military and had been appointed
High Sheriff of Clare in 1898, and justice of the peace of
Salop. According to Desmond Oulton (owner of
Clontarf Castle), his father John George Oulton had suggested to
Éamon de Valera towards the end of the
Irish Free State, that Ireland should have its own king again, as it was in the times of
Gaelic Ireland. He suggested to him, a member of the
O'Brien Clan, descended in the paternal line from
Brian Boru, a previous
High King of Ireland: the most senior representative at the time was
Donough O'Brien, 16th Baron Inchiquin. Oulton said that Donough's nephew
Conor O'Brien, 18th Baron Inchiquin, confirmed that De Valera did offer Donough O'Brien the title of Prince-President of the Irish Republic, but this was turned down and so a
President of Ireland was instituted instead. The 16th Baron was succeeded by his younger brother
Phaedrig O'Brien, 17th Baron Inchiquin, a consulting
geologist, who in turn was succeeded by his nephew, the 18th baron. Following the death of the 18th baron in 2023, the direct male line of the 15th baron failed; the 18th baron was succeeded by his second cousin. In the
Gaelic nobility, Lord Inchiquin is '''The O'Brien, Chief of the Name, Prince of Thomond'''. The family seat of the O'Brien Baronetcy was
Dromoland Castle, near
Newmarket-on-Fergus,
County Clare. The current Baron Inchiquin lives in Thomond House adjacent to Dromoland. ==Barons Inchiquin (1543)==