The 1st earl left two sons and two daughters by his second wife. The eldest son, William (1709-1764), who succeeded to the title, assumed the name of Clavering in addition to that of Cowper on the death of his maternal uncle. His wife was a daughter of the earl of Grantham, and grand-daughter of the earl of Ossory. The son of this marriage, George Nassau, 3rd Earl Cowper (1738-1789), inherited the estates of the earl of Grantham; and in 1778 he was created by the emperor Joseph II. a prince of the Holy Roman Empire. The 5th earl (1778-1837) married a daughter of Lord Melbourne, the prime minister, by whom he had two sons; and his widow married as her second husband Lord Palmerston, who devised his property of Broadlands to her second son, William Francis Cowper-Temple (1811-1888), who was created Baron Mount Temple in 1880. The elder son, George Augustus Frederick (1806-1856), 6th Earl Cowper, married Anne Florence, daughter of Thomas Philip, earl de Grey; and this lady at her father's death became _suo jure_ baroness Lucas of Cradwell. Francis Thomas de Grey, 7th Earl Cowper (1834-1905), in addition to the other family titles, became in 1871 10th Baron Dingwall in the peerage of Scotland, and 8th Baron Butler of Moore Park in the peerage of Ireland as heir-general of Thomas, earl of Ossory, son of the 1st duke of Ormonde; the attainder of 1715 affecting those titles having been reversed in July 1871. On the death of his mother he also inherited the barony of Lucas of Cradwell. On the death without issue in 1905 of the 7th earl, who was lord lieutenant of Ireland 1880-1882, the earldom and barony of Cowper, together with the viscountcy of Fordwich, became extinct; the barony of Butler fell into abeyance among his sisters and their heirs, and the baronies of Lucas and Dingwall devolved on his nephew, Auberon Thomas Herbert (b. 1876).
See _Private Diary of Earl Cowper_, edited by E. C. Hawtrey for the Roxburghe Club (Eton, 1833); _The Diary of Mary, Countess Cowper_, edited by the Hon. Spencer Cowper (London, 1864); Lord Campbell, _Lives of the Lord Chancellors and Keepers of the Great Seal_ (8 vols., London, 1845-1869); Edward Foss, _The Judges of England_ (9 vols., London, 1848-1864); Gilbert Burnet, _History of his Own Time_ (6 vols., Oxford, 1833); T. B. Howell, _State Trials_, vol. xii.-xv. (33 vols., London, 1809-1828); G. E. C., _Complete Peerage_ (London, 1889). (R. J. M.)