Cefn Mably makes up part of St Mellons. A small suburb on the east side of Cardiff, South Wales.
David the third son of John Kemeys, married Cecil, daughter and heir of Llewelyn Evan of Cefn Mably. The Cefn Mably estate remained in the hands of the Kemeys family until the death, unmarried, of Charles Kemeys in 1735.
He was succeeded by his sister Jane who married the Rev. John Tynte (d. 1710), 2nd baronet, of Halswell in Somerset, and rector of Goathurst. They were succeeded in turn by their three sons, Halsewell Tynte (1705-30), 3rd baronet, of Halswell and Cefnmabli, Rev. John Tynte (1707-1740, d. unm.), 4th baronet and rector of Goathurst, and Charles Kemeys Tynte (1710-1785, dsp.), 5th baronet.
Sir Charles Kemeys Tynte developed Halswell Park and received the Penmark estate from Mary Kemeys (c. 1699-1785) who had married William Kemeys. Charles was succeeded by his niece Jane Hassell (1738-1824), only surviving child of Charles's sister Jane Tynte (1708-41) and her husband (m. 1737) Ruishe Hassell (d. 1749), a major in the Royal Horse Guards. Jane Hassell married Colonel John Johnson of Glaiston in Rutland and Burhill, Surrey, in 1765. On his wife's succession in 1785 he changed his name to John Johnson Kemeys-Tynte (d. 1795). They were succeeded by their son Colonel Charles Kemeys Kemeys-Tynte (b. 1788) of Halswell and Cefn Mably, who was succeeded by his son Charles John Kemeys-Tynte (b. 1800), lieutenant-colonel of the Glamorgan militia and MP for West Somerset, 1832-1837, and Bridgwater, 1847-1865. He married Elizabeth, daughter and coheir of Thomas Swinnerton of Butterton Hall, Staffordshire, in 1822, and was succeeded by his son Charles Kemeys-Tynte (b. 1822), colonel of the Somerset militia. Cefn Mably remained in the hands of the Kemeys Tynte family until 1923