His maternal grandfather was the leading seventeenth-century statesman Sir John Trevor.
He was grandfather to Arthur Wellesley, 1st Duke of Wellington He represented Hillsborough in the Irish House of Commons from November 1715 and then County Down from 1727 until he was raised to the Irish House of Lords when created Viscount Dungannon and Baron Hill of Olderfleet in the Peerage of Ireland on 17 February 1766.
He married firstly Barbara Deane (who died young), of Crumlin, Dublin, daughter of Joseph Deane, Chief Baron of the Irish Exchequer; and secondly in 1737 Anne Stafford of Brownstown, County Meath (marriage settlement dated 11 January 1737/8[1]), by whom he had three children.
Their only son predeceased his father and the title passed to their grandson, Arthur Hill-Trevor, 2nd Viscount Dungannon.
Through his daughter, Anne, who married Garret Wesley, 1st Earl of Mornington, Lord Dungannon was maternal grandfather of the 1st Duke of Wellington.