- Cornelius O'Brien was the son of Henry O'Brien of Ennis, county Clare and Helen O'Callaghan of Kilgorey. In 1816 he married Margaret, daughter of Peter Long of Waterford and widow of James O’Brien of Limerick. Trained in the Law Cornelius O'Brien represented county Clare in Parliament from 1832 to 1847. He regained his seat in July 1852 and died in 1857. In the early 1850s he purchased some of the estate of the Crowe family. At the time of Griffith's Valuation he held land in six baronies of county Clare but his estate was mainly located in the parish of Kilmacrehy, barony of Corcomroe and in the parishes of Dysert and Inagh, barony of Inchiquin and Feakle, barony of Tulla Upper. His son George O'Brien entered the King's Inns in 1855 under 20 years of age and married Helen Butler of Bunnahow. George O'Brien died in 1867. The Birchfield property then passed to Cornelius Keogh by his marriage to Mary O’Brien, youngest daughter of Cornelius O'Brien. William Henry McGrath, stated to be a brother in law of George O'Brien when entering the King's Inns, came into possession of Cornelius O’Brien’s Toonagh estate by his marriage to Bridget O’Brien in 1852. George O'Brien married Ellen, daughter of William Butler of Bunnahow. She married secondly Charles Vyse of Fermoy, county Cork, who is recorded as owning 1,340 acres in county Clare in the 1870s. The estate of Charles Vyse amounting to 1,677 acres in the barony of Corcomroe including part of Birchfield and Seamount House was advertised for sale in April 1880. The sale rental gives details of the O'Brien title to the Birchfield estate.
- In 1852 William Henry McGrath married Bridget O'Brien, a daughter of Cornelius O'Brien of Birchfield, parish of Kilmacrehy, barony of Corcomroe, county Clare and they inherited the Toonagh estate. Weir writes that Elizabeth Mary, daughter of John Stacpoole O'Brien of counties Clare and Armagh was William McGrath's second wife. They had a son also named William Henry McGrath born in 1877 and a grandson Sir Brian McGrath, private secretary to the Duke of Edinburgh. In the 1870s William Henry McGrath of Toonagh and Dublin owned 3,092 acres in county Clare and a further 1,118 acres in common with Cornelius A. Keogh.
- Cornelius Alexander Keogh is recorded in the 1870s as owning 3,351 acres in county Clare and 2,023 acres in county Sligo. He also owned 1,118 acres in county Clare in common with William H. McGrath. Three addresses are given for him in Hussey de Burgh's book, Oakport, Boyle, county Roscommon, Clorkeam Lodge, county Sligo and Birchfield, Liscannor, county Clare. Cornelius Keogh married as his first wife Mary O'Brien daughter of Cornelius O'Brien of Birchfield, county Clare and following the death of his brother in law George O'Brien in 1867 came to possess the Birchfield estate. His second wife was Katie Mary Balfe, daughter of Patrick Joseph Balfe of South Park, county Roscommon. They married in 1875. The addresses given for C.A. Keogh in Burke's ''Irish Family Records'' are Oakport and Geevagh, county Sligo. He had children by his second marriage.