- Richard Tonson settled in Ireland in the latter half of the 17th century. He bought the Spanish Island estate in county Cork. Sir Bernard Burke states that his grandson, another Richard Tonson, was left a large property in 1718 by a friend of his grandfather's, Major Anthony Butler. As this Richard Tonson had no heirs he left his estates to a cousin of his mother's, Colonel William Hull, who took the surname Tonson and was created Baron Riversdale of Rathcormac in 1783. He married Rose Bernard of Castle Bernard, county Cork. Two of his sons succeeded as the 2nd and 3rd Barons. Ludlow Tonson, 3rd Baron and Bishop of Killaloe died unmarried in 1861. The title became extinct and his estates were inherited by William Thomas Jonas Stawell, second son of Colonel Alcock Stawell of Kilbrittain Castle. At the time of Griffith's Valuation the Reverend Lord Riversdale held lands in the parishes of Kilmaleery and Kilnasoolagh, barony of Bunratty Lower, county Clare and at least fifteen townlands in the parish of Rathcormack, barony of Barrymore, county Cork.
- Burke's "Landed Gentry of Ireland" (1912) traces the lineage of this family back to the 12th century. A member of the Stawell family of Devon came to Ireland in the early 17th century and was father of Reverend Jonas Stawell, Archdeacon of Ross, county Cork, who died circa 1669. From his eldest son, Anthony, descend the Stawells of Kilbrittain and from his younger son, Jonas, the Stawells of Crobeg. In the 1870s the estate of Colonel William Stawell of Kilbrittain Castle amounted to over 11,000 acres in county Cork and 318 acres in county Limerick. He was among the principal lessors in the parishes of Kilbrittain, Rathclarin, Ringrone and Templetrine at the time of Griffith's Valuation while Reverend Francis Stawell was the lessor of townlands in the parishes of Kilmaloda, Kilnagross and Nohaval. Reverend Francis Stawell also held land in the parishes of Clonfert, barony of Duhallow, Shandrum, barony of Orrery and Kilmore, Mogeely, barony of Imokilly, and Dunbulloge, barony of Cork, county Cork and in the parish of Tuogh, barony of Owneybeg, county Limerick. In the 1870s the representatives of Reverend Francis Stawell, France, owned 698 acres in county Cork. In 1861 William Thomas Jonas Alcock Stawell inherited the Lisnagar estate from his relative, Reverend Ludlow Tonson, last Baron Riversdale and Bishop of Killaloe. He assumed the name of Riversdale in 1871. In 1900 he inherited Kilbrittain from his elder brother. He died childless in 1907.
Stawell (Old Court & Crobeg)
- This branch of the Stawell family, like the Kilbrittain family, trace their descent from Archdeacon Stawell of Kinsale in the mid 17th century. They settled at Ballylought, near Mallow, county Cork. George Stawell of Summerhill, Ballylought and Ballyveniter, married his cousin, Elizabeth, daughter of Jonas Stawell of Kilbittain and in 1805 their eldest surviving son, Jonas of Old Court, married Anne Elizabeth Foster, daughter of the Bishop of Clogher. Jonas and Anne's third son became Sir William Stawell (born 1815), Chief Justice of Victoria, 1857-1886. At the time of Griffith’s Valuation, their eldest son, George Cooper Stawell of Old Court, held land in the parishes of Donaghmore and Grenagh, barony of Barretts, county Cork. In 1843 George C. Stawell married Elizabeth Tandy of Belrath, county Meath but they had no children. Over 850 acres of his estate at Ballyveniter was advertised for sale in October 1851 and again in July 1852. George Stawell of Crobeg, county Cork, was a younger brother of Jonas Stawell of Old Court. In 1801 he married Elizabeth Longfield of Longueville and in the 1870s their son, George Stawell of Crobeg, owned 3,222 acres in county Cork. At the same time another family member, Jonas Stawell of Gurrane, younger brother of George Cooper Stawell, owned 1,257 acres. In March 1865, property in Cork City belonging to John Robert Stawell was sold in the Landed Estates Court to John Russell.