His mother worked to ensure the land would be passed on to Donat by marrying a Cromwellian soldier named John Cooper, by whom she had a son Henry, at least eight years later.

His younger daughter, Elizabeth later died, aged 18, in 1697, leaving Donat with only his two sons, Lucius and Henry.

The widow of the 7th Earl of Thomond assigned the freehold of Dromoland Castle to Donat, and from 1684 onwards it remained the property of the Leamaneh O'Briens.

He captained a group of Dragoons in Clare numbering about 20 men in this time, to protect himself and his neighbours from rapparees.

He negotiated the marriage of his eldest son and heir, Lucius, in 1701 to Catherine, daughter of Thomas Keightley, an uncle in law of Queen Anne.

He died on 17 November 1717 and was interred at Kilnasoolagh Church, where there is a marble effigy and monument, erected by his son Henry.

The Latin inscription reads: Pause on your Way and Look Beneath this Marble is hidden the Mortal Part of DONATUS O’BRIEN Baronet Who by the Lineage of his Forefathers was Noble By his own Virtues far Nobler A Man truly made for Humanity Wholly born for Faith, Friendship, Favour In Bodily Stature he was Tall and Handsome The Dignity in his Aspect, the Majesty in his Speech The Gravity in his Gait, the Simplicity in his Manners Were Tokens of Prudence, Calmness, Authority As a Father you could see none more Indulgent As a Grandfather none more Kindly As a Husband none more Loving As a Friend none more True The Public Highways and Bridges prove him a Protector of Trade The Decorations of the Parish Church bespeak him truly its Son An Orthodox Clergyman disturbed by Impious Strife Cast out from his Benefice and by Wicked Violence bereft of his Flock Found Shelter in his House (whenever the Wickedness of the Times required) Thus showing Danger to Himself and his Neighbours Thus showing Charity to his Brother Man and his Zeal for his Religion For these Merits Fortune heaped Rewards on him His so conspicuous Virtues were adorned by Wealth and Honour He was a Member of the Royal Privy Council under Queen Anne His Patrimony, honestly and notably increased, he bequeathed to his Children To all Good Men he left Grief for his Loss He died on the 18th day of November 1717 in the 76th year of his Age This Monument as a Lasting Memorial of true and Sincere Goodness was placed here by Henry His second and only surviving Son At his own Expense.