Background
He was part of the O'Neill dynasty of Ulster, the illegitimate son of Matthew O'Neill, 1st Baron Dungannon.
He was part of the O'Neill dynasty of Ulster, the illegitimate son of Matthew O'Neill, 1st Baron Dungannon.
He was the half-brother of Brian O'Neill, Cormac MacBaron O'Neill and Hugh O'Neill, Earl of Tyrone. Art MacBaron (his middle name a reference to the title of his father) ruled over Oneilland south of Lough Neagh. He could speak fluent English unlike many of his relations.
He fought alongside the Earl during Tyrone's Rebellion (1594-1603). He died in 1618. He had nine sons, one of whom was Owen Roe O'Neill who served as a mercenary in the Spanish Army for many years before returning to Ireland during the Irish Confederate Wars. The two remaining sons also served in the Spanish Army.