On 17 June 1786, he married secondly Mary Monckton, daughter of the 1st Viscount Galway: her salon was one of the centres of intellectual life in London for half a century.
He had also an illegittimate son with Julia Fane, wife of Robert Monckton; their son was the 1st Viscount Galway.
Pitt resigned as governor in 1735 with a considerable fortune, purchased what later became known as Orleans House Twickenham from the estate of James Johnston who died in 1737 and bought in January 1740 burgages and freeholds from Sir William Lowther which with Lord Galway's interest gave complete control of the Pontefract seat.
The first house on the site was built 1740 by James Paine for John Monckton, 1st Viscount Galway, who had bought the 500 acre Serleby estate from the Saunderson family of Blyth.
The fourth creation came in the Peerage of Ireland in 1727 when John Monckton was made Baron Killard, of the County of Clare, and Viscount Galway.
County Galway | Galway | Louis Mountbatten, 1st Earl Mountbatten of Burma | Horatio Nelson, 1st Viscount Nelson | Viscount | Herbert Kitchener, 1st Earl Kitchener | Vickers Viscount | Charles Cornwallis, 1st Marquess Cornwallis | 1st United States Congress | Frederick Roberts, 1st Earl Roberts | Bernard Montgomery, 1st Viscount Montgomery of Alamein | William Cecil, 1st Baron Burghley | Robert Harley, 1st Earl of Oxford and Earl Mortimer | George Villiers, 1st Duke of Buckingham | William Howe, 5th Viscount Howe | Thomas Wentworth, 1st Earl of Strafford | William Pitt, 1st Earl of Chatham | viscount | Joseph Lister, 1st Baron Lister | Robert Baden-Powell, 1st Baron Baden-Powell | John Scott, 1st Earl of Eldon | Henry Brougham, 1st Baron Brougham and Vaux | Edward Seymour, 1st Duke of Somerset | Robert, 1st Earl of Gloucester | James Galway | Guy Carleton, 1st Baron Dorchester | Garnet Wolseley, 1st Viscount Wolseley | Douglas Haig, 1st Earl Haig | George Monck, 1st Duke of Albemarle | Frederick Schomberg, 1st Duke of Schomberg |