Stewart’s Whig father James, whose family had long held one of the principal electoral interests in Tyrone, represented his county at Dublin and Westminster from 1768 to 1812. William regained the seat at the general election of 1818 with the support of local magnates and Lord Liverpool’s administration, but sided with opposition in the Commons, except (following his father’s example) on Catholic relief.
He confidently asserted in his address that he would be well enough to attend Parliament, nothing came of a rumoured challenge and he was returned unopposed at the general election of 1826.
In his youth Stewart had lived for some years with Ellen, daughter of Edmund Power of Curragheen, county Waterford, with whom he had had three daughters. She afterwards married John Home Purves, a younger son of Sir Alexander Purves of Purves Hall, Berwickshire, who passed off the children as his own, although, as Greville noted, ‘nothing could be more notorious than the original connection and the real paternity’. Later still she married the Commons Speaker Charles Manners Sutton, so ending her days (in 1845) as Viscountess Canterbury.
