Fergal Mág Tighearnán, the Third

On the death of the previous clan leader, Fergal took the chieftaincy and resided in the castle of Croaghan of the Cups (Irish: Cruachan O'Cúbhrán, now the townland of Croaghan), now in the townland of Coolnashinny, beside the modern town of Killeshandra.

In 1582 O'Rourke, the High Sheriff of Leitrim and the English attacked the McKiernans.

The Annals of Loch Cé for the year 1582 state:

Another depredation was committed by the sheriff O'Ruairc, and by the Saxons along with him, upon the sons of Mac Tighernain of the Breifne, at Loch-Roda; and their women were borne off captives from them.

On 7 November 1587 John McKiernan, the under-sheriff of County Westmeath,[2] a native of Aghaweenagh in Tullyhunco, petitioned the government to appoint him the seneschal of Tullyhunco in order to civilise the natives.[3]

Nov. 7. 4. Petition of John Kernan to Burghley. Humbly beseecheth your honourable Lordship, your orator, John Kernan, of Aghewehan, in the territory or cantred of Tolconchoe, alias M'Kernan's country, in the county of the Cavan, within the realm of Ireland, that it may please your Lordship with your favour to further his petition to Her Majesty for the grant of the reversion of the office of Clerk of Common Pleas in the Exchequer for his life, and of the seneschalship of the said cantred to him and to his heirs males of his body, in consideration of his endeavours in Her Majesty's service in the government of Sir William Fytzwylliams, Arthur Lord Grey, and the Lords Justices [Loftus and Wallop], and the rather that your said orator, through the entreaty of his kinsmen, the inhabitants of the said cantred, has left the English Pale to dwell among them, hoping, if convenient countenance be afforded to him by the said grant, to bring them, through dutiful exhortation, and examples of husbandry and other civil trades, from their disorders and disobedience to the due regard of loyalty and obedience. Your said orator presenteth unto your honourable Lordship the opinion and testimony of the Lord Grey and Sir William Fytzwylliams touching your orator by their several letters unto Mr. Secretary Walsyngham, being required so to do by his Honour, at his last being at the Court, since which time your orator hath dutifully attended your Honours and the other Lords of Her Majesty's most honourable Council for Her Majesty's most gracious pleasure in his said suit, and yet some seeking the disgrace of your orator have rumoured that he is suitor for the seneschalship of Meath and Westmeath long since, with the liberty and jurisdiction palatine of the said counties determined and annulled by parliament. Your orator's poor suit is none other than as hereby is declared, a matter of small profit to your orator and less charge to Her Majesty, and in regard thereof moved rather than anything more chargeable to Her Highness, whereof your orator hopeth that your Honour in your grave judgment will think him worthy.

He was granted the position by Fiant No. 5156 on 20 March 1588[4]

Grant to John Kearnan, gent; of the office of seneschal of the territory of Upper Talconchoe alias M’Kearnans country in co. Cavan. To hold during good behavior, with all accustomed profits. With power to raise the inhabitants, and command them for defence of the territory, the public weal of the inhabitants, and the punishment of malefactors; to prosecute, banish, and punish by all means malefactors, rebels, vagabonds, rymors, Irish harpers, bards, bentules, carrowes, idle men and women, and those who assist such; and twice a year within a month after Easter and Michaelmas respectively to hold a court and law day. He shall not take any unlawful Irish exactions from the inhabitants, as to cess them with kern, nor impose coney or livery, without direction of the Lord Deputy.

The Annals of Loch Cé for the year 1588 state: "Mac Tighernain of the Breifne, i.e., Ferghal, died."