In 1723 he was created Viscount Darnley of Athboy, and in 1725 Earl of Darnley, both in the peerage of Ireland. He also succeeded to the title of Baron Clifton of Leighton Bromswold, in the peerage of the United Kingdom, by which title he and his successors sit in the House of Lords. His lordship was succeeded, as second Earl of Darnley, by his son, who was again, on his death, succeeded by his son John, as third earl. This nobleman, who was born in 1719, married in 1766 Mary, daughter and heiress of John Stoyt, of Street, co. Westmeath, and by her, who died in 1803, had issue John, afterwards fourth earl; Lady Mary, married to Sir Lawrence Palk, Bart.; the Hon. Edward Bligh, a general in the army; Lady Theodosia, married to her cousin, Thomas Cherbourgh Bligh; Lady Catherine, married to Hon. Charles William Stewart, afterwards Marquis of Londonderry; and the Hon. William, a colonel in the army. The Earl died in 1781, and was succeeded by his son John, as fourth earl. He married, in 1791, Elizabeth, daughter of the Right Hon. William Brownlow of Lurgan, and by her had issue Edward, fifth earl; Lady Mary, married to Charles Brownlow, Esq.; Hon. John Duncan Bligh, Secretary of Legation at St. Petersburgh; and the Lady Elizabeth, married to the Rev. J. Brownlow. His lordship died in 1831, and was succeeded by his son Edward, fifth earl, who (born in 1795), married in 1825 Emma Jane, third daughter of Sir Henry Brooke Parnell, Bart., M.P.,—who, having held office as Secretary at War, Paymaster-General of the Forces, and Treasurer of the Navy and Ordnance, was created Baron Congleton in 1841,—and sister to the present Lord Congleton. By this lady, who is still living, his lordship had issue, John Stuart Bligh, sixth and present earl of Darnley; the Hon. and Rev. Edward Vesey Bligh; the Hon. and Rev. Henry Bligh; the Lady Elizabeth Caroline, and the Lady Emma Bess, both of whom are married and bear the name of Cust—the first being the wife of Reginald Cust, Esq., and the latter the wife of the Rev. Arthur Perceval Purey-Cust. His lordship died in 1835, and was succeeded by his eldest son, John Stuart Bligh, as sixth earl.