They had six children (of whom three died young): In 1661, he represented County Clare in the Parliament of Ireland, and from 1670 until his death in 1678, Northampton.
His wife's relationship with Charles II gave them a valuable opening at Court, where they already had a friend in Sir Joseph Williamson and they enjoyed high favour in the 1660s.
His courtesy title passed to his younger half-brother Henry Horatio O'Brien, Lord Ibrackan.
The speed of her remarriage gave rise to unkind rumours that the pair had been lovers, and the marriage was disapproved of, even by her children, since Williamson, the son of a country vicar, was not considered a suitable match for a connection of the King.
He is a major character in The Piccadilly Plot, the seventh in the Thomas Chaloner mystery novels by Susanna Gregory.