Hello, I have researched this Brehony family and have the following info on descendants of Patrick Brehony and Margaret Glynn of Derreenavoggy:
Thomas (born 1865) emigrated to the Jordan Valley in Marheur county Oregon, USA where he worked in sheep ranching. He remained single and died 20 April 1927 in the Vale Sanatorium, Vale, Malheur, Oregon, USA
Terence (born 1866) married Mary Anne Christie from nearby Upper Rover near Arigna on Feb 14, 1901 in East Calder, Scotland. They lived in Uphall near Broxburn in 1901 and in Broxburn in 1911 where he worked in the oil shale mines. They had 10 children and he died age 59 of meningitis on 14 October 1925 in the Royal Infirmary Edinburgh, Scotland
Bridget (born 1868) was attending her mother Mary Glynn's death in Arigna in 1909, living with her sister Mary Brehony Gilvarry in the 1911 census in Londonderry, Northern Ireland (Mary's first husband was Patrick Gilvarry) and died single September 18, 1954 • Navenny Street, Ballybofey, Stranorlar, Donegal, Ireland.
Eleanor (born 1869) married Thomas Wynne (born Guihen, spelling of last name changed) from neighboring Carrownalth on January 17, 1899 in the Chapel of St. Malachy, Belfast Rosemary St Church, Antrim, Northern Ireland and they lived in Hamilton, Scotland having 7 children and she died 20 March 1936 in Hamilton, Midlothian County, Scotland.
Patrick (born 1873) also went to the Broxburn area in Scotland marrying Catherine Davidson Heatie in 1910 at the St. Andrews Church in Edinburgh and they had 3 children before she died two days after giving birth to son James. About 1917 he married Catherine Dignon. He worked as an insurance agent, although he went to Oregon for a brief stint in 1926 to try his hand at gold mining. Lots of Maguire cousins living in this area, he went to join cousin William Mcguire. He returned to Scotland died 26 May 1959 in Broxburn, Scotland
Other children of Patrick Brehony and Margaret Glynn that I know of are: John born 1871, Charles born 1877 and Mary Anne born about 1880. You did not specifically ask for information regarding them, would you be interested in more info regarding those children?