The excellent site of Timothy William Ferres tells us of the Hamiltons, of Stackallen in County Meath:
GUSTAVUS HAMILTON (1642-1723), having abandoned the fortunes of JAMES II, to whom he was a privy counsellor, and distinguished himself as a military officer in the service of WILLIAM III, particularly at the battle of the Boyne, and the siege of Derry, was sworn of the Privy Council of the latter monarch, appointed Brigadier-General of his armies, and further rewarded with a grant of forfeited lands. General Hamilton was MP for County Donegal, 1692-1713, and for Strabane, 1713-15. He was elevated to the peerage, 1715, in the dignity of Baron Hamilton of Stackallan, County Meath. His lordship was advanced to a viscountcy, in 1717, as VISCOUNT BOYNE.
He married Elizabeth, second daughter of SIR HENRY BROOKE, Knight, of Brookeborough, County Fermanagh. They had issue:
FREDERICK (c. 1663-1715), father of GUSTAVUS, 2nd Viscount; Gustavus, father of 3rd and 4th Viscounts; Henry, MP for Donegal, 1725-43; Elizabeth.
The 1st Viscount was succeeded by his grandson, GUSTAVUS, 2nd Viscount (1710-46).
Gustavus 2nd Viscount died unmarried, and the honours devolved upon his cousin, Frederick, 3rd Viscount (1718-72).
James Hamilton (1559/1560 or 1568-1643) 1st Viscount Clandeboye married Ursula, daughter of Edward Brabazon, 1st Lord Brabazon, Baron of Ardee. They had no children and after her death he married Jane Philipps, who gave birth to their heir James Hamilton (1617/18-1643) 1st Earl of Clanbrassil, County Armagh.
James Hamilton (1617/18-1643) 1st Earl of Clanbrassil married Anne Carey (d. 1688/89), who gave birth to their heir Henry Hamilton (1647-1675), 2nd Earl of Clanbrassil. They had no children and after his death the title became extinct. The name Claneboye was revived in a title in 1800 when his great-great-grandniece Dorcas Blackwood was made 1st Baroness Dufferin and Claneboye.
There were lots of creations of Earls of Clanbrassil! There was James Hamilton (1697-1758) 1st Earl of Clanbrassill, Co. Armagh. He was the son of James Hamilton (d. 1693) and Anne Mordaunt.
James Hamilton (1575-1618) 1st Earl of Abercorn, Co. Linlithgow [Scotland] was Member of the Council of the province of Munster on 20 May 1615. His son Claud Hamilton (d. 1638) was created 2nd Lord Hamilton, Baron of Strabane, County Tyrone. Another son was the heir, James Hamilton, 2nd Earl of Abercorn. The 2nd Earl had a son, George Hamilton who became 3rd Earl of Abercorn but had no children.
Claud Hamilton (d. 1638) 2nd Lord Hamilton, Baron of Strabane, County Tyrone was succeeded by his son James Hamilton (1633-1655) 3rd Lord Hamilton, Baron of Strabane but he died without issue and was succeeded by his brother, George Hamilton (d. 1668) 4th Lord Hamilton, Baron of Strabane.
George’s son Claud Hamilton (1659-1691) succeeded as 5th Lord Hamilton, Baron of Strabane, Co. Tyrone and 4th Earl of Abercorn. He held the office of Lord of the Bedchamber to King James II. He fought in the Battle of the Boyne on 1 July 1690. On 11 May 1691 he was outlawed in Ireland, and his Irish titles were forfeited. He fought in the Battle of Aughrim on 12 July 1691, where he commanded a regiment of horse. [1]
Claud Hamilton (1659–1691) 4th Earl of Abercorn didn’t have offspring and was succeeded by his brother, Charles (d. 1701) who became 5th Earl of Abercorn. His brother John (1713/4-1755) had a son, John James Hamilton, who succeeded as 5th Baronet Hamilton, of Donalong, Co. Tyrone and of Nenagh, Co. Tipperary, 9th Earl of Abercorn, and was later created 1st Marquess of Abercorn.
With his death, the senior line of the Abercorns and the Strabanes failed as he had no surviving offspring. With regard to the Abercorns, the succession reverted to the next of the cadet branches descending from the five sons of the 1st Earl of Abercorn as it already had done in about 1650 when George, the 3rd Earl, died unmarried in Padua. As the 1st Earl’s third son, William, 1st Baronet of Westport, had no children, the succession passed to the descendants of the fourth son, Sir George Hamilton (d. 1679) 1st Baronet, of Donalong, County Tyrone and his wife Mary Butler (d. 1680) daughter of Thomas Butler Viscount Thurles. The 5th Earl was therefore succeeded as Earl of Abercorn by his second cousin, James Hamilton (d. 1734) the grandson of Sir George. James Hamilton would thus become the 6th Earl of Abercorn.
James Hamilton, 6th Earl of Abercorn, also 2nd Baronet Hamilton, of Donalong, Co. Tyrone and of Nenagh, Co. Tipperary and 1st Baron Mountcastle, Co. Tyrone was succeeded by his son, James Hamilton, (1685/6-1743/4) 7th Earl of Abercorn, who was succeeded by his son, James Hamilton (1712-1789) 8th Earl of Abercorn, who died unmarried.
The next in line was John James Hamilton (1756-1818) who succeed as 5th Baronet Hamilton, of Donalong, Co. Tyrone and of Nenagh, Co. Tipperary, 9th Earl of Abercorn and was later created 1st Marquess of Abercorn. He was the posthumous son of Captain Hon. John Hamilton and his wife Harriet, and grandson of James Hamilton, 7th Earl of Abercorn
John James Hamilton (1756-1818) 1st Marquess of Abercorn married first Catherine Copley and they had several children including a son James (1786-1814), called Viscount Hamilton. He married Harriet Douglas who gave birth to their heir James Hamilton (1811-1885), who was to become 1st Duke of Abercorn.
John James Hamilton (1756-1818) 1st Marquess of Abercorn married secondly a cousin, Cecil Hamilton, but they later divorced. He then married Anne Jane Gore, daughter of Arthur Saunders Gore, 2nd Earl of Arran of the Arran Islands.
[1] G.E. Cokayne; with Vicary Gibbs, H.A. Doubleday, Geoffrey H. White, Duncan Warrand and Lord Howard de Walden, editors, The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Extant, Extinct or Dormant, new ed., 13 volumes in 14 (1910-1959; reprint in 6 volumes, Gloucester, U.K.: Alan Sutton Publishing, 2000), volume I, page 4. Hereinafter cited as The Complete Peerage.