He succeeded his father in the earldom in 1663. Like most of his family, both Brudenells and Treshams, he was an adherent of Roman Catholicism. His father's devotion to that faith was so open that he was prosecuted regularly for recusancy. In 1613 the local justices of the peace remarked that only their personal regard for the Brudenell family had saved fourteen of them, including Robert's parents, from prison. His mother's family were deeply implicated in the Gunpowder Plot.[1]
Robert himself and his eldest son Francis, as two of the most influential members of the Catholic nobility, inevitably became the target of informers, particularly William Bedloe, during the Popish Plot:[2] Robert retired to France for a time, while his son spent a year in prison.[3]
Francis Brudenell, Lord Brudenell (d. 1698), eldest son and heir apparent, who predeceased his father, having married Frances Savile, a daughter of James Savile, 2nd Earl of Sussex, by whom he had two sons and three daughters: