His first wife was Margaret, eldest daughter of Hugh O'Neill, Earl of Tyrone, who was the most powerful Roman Catholic noble in the country at the time.
At the commencement of hostilities in the Irish Rebellion of 1641, he appeared inclined to espouse the Government side, and was appointed joint Governor of Kilkenny with the earl.
Fearing, however, that the rights and liberties of his Catholic brethren would be still further interfered with, he wrote an explanatory letter to the Earl and took possession of Kilkenny in the name of the Confederates.
He then detached parties to secure other adjacent towns, which was done with such success that in the space of a week all the fortresses in the counties of Kilkenny, Waterford, and Tipperary were in their power.
The Viscount's forces were thereby considerably weakened, and he was defeated by the Earl of Ormonde at the Battle of Kilrush, near Athy, on 10 April 1642.