Hugh Boy, son of Donnell Og O'Neill, grandson of Aodh Meith O'Neill (Hugh the Fat), and great-grandson of Áed in Macáem Tóinlesc, all kings of Cenél nEógain of the Northern Uí Néill, was the eponymous ancestor of the O'Neill Clandeboye, line.
He had come to an arrangement with the Norman Earls of Ulster which allowed his sons, particularly Brian, to consolidate O'Neill power within The North at the expense of the O'Donnells.
Hugh Boy was married Eleanor de Nangle, a kinswoman to his nominal enemy, Walter de Burgh, the Earl of Ulster and Jocelyn de Angulo; Hugh died in 1283.
The lineage he established remained senior among the O'Neill's, becoming semi-independent with a distinct territory.
Having helped the Anglo-Normans barons in a rebellion against their fellow Norman lord, the Earl of Ulster, the family was granted land outside the North, in Ulster within what is now south County Antrim.
That was the official establishment of the Lordship of Cloinne Aodha Buidhe, or the O'Neills of Clandeboye, though the English retained lordship over the much-reduced Earldom of Ulster.

The family fought on both sides of the wars that racked Ireland from the 1530s to 1690s, whose end result was a significant loss of territory and influence due to political alliances and an influx of new families flowing in from Scotland and England.

The issue of Sir Henry O'Neill, who had been granted the Edenduffcarrick estate and majority of the Clandeboye lands by conforming to English ways and converting to Anglicanism, died out in 1855.
At this time, the barrister Charles Henry O'Neill of the O'Neills of the Feevah, descendant of the last tanasite of Clandeboye, Sir Henry's uncle Con Mac Brian O'Neill, became officially recognized as The O'Neill Clanaboy. "
The descendants of Prince Con MacBryan O'Neill, Tanist of Clanaboy, remained loyal, under every vicissitude, to the traditions of their house, and saved little out of the general wreck of confiscation.
They seemed to have preferred fulfilling the solemn pledge of their ancestor, Donald O'Neill, King of Ulster, to 'fight out as long as life should last' rather than adapt themselves to altered circumstances, as the descendants of Shane MacBryan had wisely done," according to Burke's Peerage.
In fact both Sir Henry and his daughter Rose willed the Shane's Castle estate to the descendants of Prince Con mac Brian.
While Charles Henry assumed the title, the Clandeboye O'Neill estate was passed to William Chichester through his grandmother Mary O'Neill – a move highly disputed.
Charles Henry O'Neill had his first and only child, a daughter named Elizabeth Catherine Theresa Mary O'Neill, in 1845, during the Great Hunger, and had no further issue.
From the death of Charles Henry O'Neill until Jorge O'Neill assumed the chieftainship the family had no chief.
Hugh Boy, son of Donnell Og O'Neill, grandson of Aodh Meith O'Neill (Hugh the Fat), and great-grandson of Áed in Macáem Tóinlesc, all kings of Cenél nEógain of the Northern Uí Néill, was the eponymous ancestor of the O'Neill Clandeboye, line. He had come to an arrangement with the Norman Earls of Ulster which allowed his sons, particularly Brian, to consolidate O'Neill power within The North at the expense of the O'Donnells. Hugh Boy was married Eleanor de Nangle, a kinswoman to his nominal enemy, Walter de Burgh, the Earl of Ulster and Jocelyn de Angulo; Hugh died in 1283. The lineage he established remained senior among the O'Neill's, becoming semi-independent with a distinct territory. Having helped the Anglo-Normans barons in a rebellion against their fellow Norman lord, the Earl of Ulster, the family was granted land outside the North, in Ulster within what is now south County Antrim. That was the official establishment of the Lordship of Cloinne Aodha Buidhe, or the O'Neills of Clandeboye, though the English retained lordship over the much-reduced Earldom of Ulster.
The family fought on both sides of the wars that racked Ireland from the 1530s to 1690s, whose end result was a significant loss of territory and influence due to political alliances and an influx of new families flowing in from Scotland and England.
The issue of Sir Henry O'Neill, who had been granted the Edenduffcarrick estate and majority of the Clandeboye lands by conforming to English ways and converting to Anglicanism, died out in 1855. At this time, the barrister Charles Henry O'Neill of the O'Neills of the Feevah, descendant of the last tanasite of Clandeboye, Sir Henry's uncle Con Mac Brian O'Neill, became officially recognized as The O'Neill Clanaboy. "The descendants of Prince Con MacBryan O'Neill, Tanist of Clanaboy, remained loyal, under every vicissitude, to the traditions of their house, and saved little out of the general wreck of confiscation. They seemed to have preferred fulfilling the solemn pledge of their ancestor, Donald O'Neill, King of Ulster, to 'fight out as long as life should last' rather than adapt themselves to altered circumstances, as the descendants of Shane MacBryan had wisely done," according to Burke's Peerage. In fact both Sir Henry and his daughter Rose willed the Shane's Castle estate to the descendants of Prince Con mac Brian. While Charles Henry assumed the title, the Clandeboye O'Neill estate was passed to William Chichester through his grandmother Mary O'Neill – a move highly disputed. Charles Henry O'Neill had his first and only child, a daughter named Elizabeth Catherine Theresa Mary O'Neill, in 1845, during the Great Hunger, and had no further issue. From the death of Charles Henry O'Neill until Jorge O'Neill assumed the chieftainship the family had no chief.
O'Neill dynasty