Cathbarr's elder brothers Donnell and Hugh Roe were rivals in the lengthy Ó Domhnaill succession dispute until Donnell's death at the Battle of Doire Leathan in 1590. Hugh Roe became head of the Ó Domhnaills in 1592. Cathbarr supported his elder brother during Tyrone's Rebellion (1594–1603). In 1602 another elder brother Rory succeeded Hugh Roe and made peace with the Crown. The following year Rory was made Earl of Tyrconnell.
After Cathbarr's death, Rosa remarried to the Irish soldier Owen Roe O'Neill. Cathbarr's son with Rosa, Hugh O'Donnell became a Captain in the Spanish Army, serving in his stepfather's regiment in Flanders. He was killed in 1625 during the Siege of Breda.[2]
Wife: Rosa (c.1588–1660) the daughter of Sir John O'Doherty — married secondly Owen Roe O'Neill (c. 1585–1649) who she met in the Low Countries
Hugh O'Donnell (died 1625), became a captain in the Spanish Army, serving in Flanders in the regiment of his stepfather (Owen Roe O'Neill). He was killed during the Siege of Breda.[vii]
^ abIf the Earldom of Tyrconnell had not been attained, then next in line as 3rd Earl of Tyrconnell would have been Dómhnall Óg son of Sir Donnell O'Donnell (an elder half brother of the 1st Earl)
^ abc"Hugh Albert O'Donnell, born [to Rory and Brigid] about October 1606, was the only son of this marriage, Mary Stuart O'Donnell being born about a year later. Some authorities give an eldest child, Elizabeth, probably illegitimate, who became first wife of Luke Plunkett, first earl of Fingall" (Silke 2006).
Burke, Sir Bernard (1866), A Genealogical History of the Dormant: Abeyant, Forfeited, and Extinct Peerages of the British Empire, Harrison, pp. 409–410
Canny, Nicholas (January 2008) [2004], "O'Neill, Hugh , second earl of Tyrone (c.1550–1616)", Oxford Dictionary of National Biography (online ed.), Oxford University Press, doi:10.1093/ref:odnb/20775(Subscription or UK public library membership required.)
Casway, Jerrold (1984), Owen Roe O'Neill and the Struggle for Catholic Ireland, University of Pennsylvania Press
Silke, John J. (May 2006) [2004]. "O'Donnell, Rury , styled first earl of Tyrconnell (1574/5–1608)". Oxford Dictionary of National Biography (online ed.). Oxford University Press. doi:10.1093/ref:odnb/20559. (Subscription or UK public library membership required.)
