Background
He was the only son of Thomas FitzWilliam, 4th Viscount FitzWilliam and his first wife Mary Stapleton, daughter of the statesman Sir Philip Stapleton.
He was the only son of Thomas FitzWilliam, 4th Viscount FitzWilliam and his first wife Mary Stapleton, daughter of the statesman Sir Philip Stapleton.
The FitzWilliam family are recorded in Ireland from about 1210, and had become one of the largest landowners in Dublin. In 1711, he built Mount Merrion House in Dublin. His older family home of Merrion Castle, was, rather surprisingly, allowed to decay: it was a ruin by 1730, and was pulled down later in the century.
Richard spent his later years in England, but his heirs returned to Mount Merrion.
Lord Fitzwilliam married Frances Shelley, daughter of Sir John Shelley, 3rd Baronet of Michaelgrove. They had five children:
Richard FitzWilliam, 6th Viscount FitzWilliam
William, Usher of the Black Rod in Ireland
John
Mary, who married Henry Herbert, 9th Earl of Pembroke
Frances, who married George Evans, 2nd Baron Carbery.
Through Fitzwilliam"s daughter Mary, Countess of Pembroke, the great FitzWilliam inheritance in Dublin passed into the Herbert family in the following century. They are still substantial landowners in Dublin.
He succeeded to the Viscountcy of FitzWilliam in 1704, and became a member of the Irish Privy Council in 1715. He was elected Member of Parliament for Fowey in 1727, a seat he held until 1734.