Séan O'Neill, the Proud, an Díomais

http://en.wikipedia.org/wiki/Shane_O%27Neill

At least three wives and several mistresses, including Agnes Campbell.

https://en.wikipedia.org/wiki/Shane_O%27Neill_(Irish_chieftain)

Séan Ó Néill, anglicised Shane O'Neill (c. 1530 – 2 June 1567), nicknamed 'Séan an díomais', was an Irish king of the O'Neill dynasty of Ulster in the mid 16th century. Shane O'Neill's career was marked by his ambition to be The Ó Néill Mór - Sovereign of the dominant Ó Néill Mór family of Tyrone... and thus head overking or Rí ruirech of the entire province. This brought him into conflict with competing branches of the O'Neill family and with the English government in Ireland, who recognised a rival claim. Shane's support was considered worth gaining by the English even during the lifetime of his father Conn O'Neill, 1st Earl of Tyrone (died 1559). But rejecting overtures from Thomas Radclyffe, 3rd Earl of Sussex, the lord deputy from 1556, Shane refused to help the English against the Scottish settlers on the coast of Antrim, allying himself instead with the MacDonnells, the most powerful of these immigrants.

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Shane had at least ten sons by his wives, as well as possible other offshoots. Many of them were fostered in O'Neill relations and vassals after their father's death, and they became the rival force to Hugh O'Neill in his climb to power in the 1580–1600 time frame.

His known children were:

Shane Og, whose mother was Catherine MacDonnell. He was tanist to Turlough Luineach, in 1579, and was killed by the O'Reilly's after an unsuccessful raid in Breifne in 1581.
Henry MacShane O'Neill, whose mother was Catherine MacDonnell. Father of Sir Henry Ó Néill and Con Boy McHenry. Perhaps the most famous of Shane's sons, he was given a large Estate in Orior County, Armagh. He died in 1622.
Conn MacShane O'Neill, whose mother was either Catherine MacLean or the daughter of Shane Óg Maguire. He invaded Ulster in 1583 with 3,000 Scottish soldiers and was named Tanist of the O'Neill, Turlough Luineach, in the 1580s. During the Nine Years' War he fought against his cousin the earl and was given a large estate (1,500 acres [6.1 km2]) and the manor lordship of Clabbye in Fermanagh. He played a part in Ulster politics until his death in 1630/1. Two of his grandsons were made Spanish counts.
Turlough, whose mother was Catherine MacDonnell of the Route. He died 1598.
Hugh Gaveloch, the most popular of the Mac Shanes, led an army of his McLean kinsmen into Ulster to support his claim to the O'Neill Mór title, but was captured and hanged by his first cousin, Hugh, Earl of Tyrone. He died in 1590.
Niall, whose mother is thought to have been Catherine O'Donnell.
Art, whose mother was Catherine MacLean; he died of exposure after escaping from English captivity in a heroic trek from Dublin Castle through snow-covered Dublin and Wicklow with Red Hugh O'Donnell at Christmas 1592.
Brian Laighneach, whose mother was Catherine MacLean. He died after 1598.
Edmond, died fighting against Hugh O'Neill, Earl of Tyrone.
Cormac, whose mother was Catherine MacLean, stayed with his brother Hugh MacShane, as did his son Cormac Boy (Buidhe). He died after 1603.
Rose, who married Conn O'Donnell of Lifford.
Possible:

Hugh McShane O'Neill, whose mother was Catherine MacLean, became chief of the O'Neill sept inside Glenconkeyne forest. Hugh's parentage is however uncertain. Several other McShane's are listed in pardons issued by letters patent on 20 October 1609, with one listed as being "McShane McOwen", suggesting that their Shane was the son of an Owen O'Neill rather than Conn Bacagh.