- The O'Briens were settled in the Castlelyons locality of county Cork from the 17th century. At the time of Griffith's Valuation Cornelius O'Brien held land in the parish of Castlelyons. He was married to Katherine Coppinger of Rossmore and they had a daughter, Cornelia. In December 1854 the Kilcor estate amounting to 1,427 acres was advertised for sale in the Encumbered Estates' Court. It was held under a lease dated 1666 from Richard Earl of Barrymore to Donogh O'Brien of Coylnacurra (Kilcor), county Cork, for 1,000 years. The rental includes a lithograph of Kilcor Castle, which is described as a modern and picturesque building in good repair. The Freeman's Journal gives details of the purchasers. In the 1870s Cornelius O'Brien of Fermoy owned just 10 acres in the county. The website www.copinger.org.uk/2Thomas4.html gives details of marriage connections between the O'Brien and Coppinger families.
- Hajba writes that Francis Doyne Dwyer bought Kilcor Castle, county Cork, from Cornelius O'Brien in 1851 [possibly 1854]. Francis Dwyer of Kilcor and Henry Dwyer of Ballyquirk were sons of John Dwyer, secretary to John Fitzgibbon Earl of Clare and a major in the Austrian Imperial Army. In June 1852 the lands of Boher and Ballylea, barony of Owney and Arra, county Tipperary, the estate of Francis Dwyer, were advertised for sale. In the 1870s Henry Dwyer of Kilcor owned 1,388 acres in county Cork and John D. Dwyer of Ballyquirk owned 696 acres in county Tipperary. In July 1852 the estate of William Barry Dwyer at Slymanagh and Curraghanaltig, barony of Fermoy, was advertised for sale. http://www.oocities.com/layedwyer/ballyquirk.htm