Denise -- Your Thomas McGeough was born, I believe, on 14 December 1880 in Dundalk. He was the eldest of a large family who resided first on Jocelyn Street, and indeed later on Kelso Terrace (cf. 1911 Census -- Kelso Terrace). Previously, I had traced the fortunes of a younger brother of his -- James McGeough. James McGeough went to Belfast before World War 1, and was a painter of boats (probably in the shipyard). Then, during the war, he came to America. According to his 1917 Selective Service registration, which I located -- he was at that time residing in Manhattan with my grandfather Edward Duffy's older brother John Duffy (who had recently been widowed). Then, in subsequent years, James (who remained single) became a crew member on the "Presidential Lines" - passenger ships like the "Coolidge" in their Pacific voyages. He continued to do this kind of work until his death in the 1950's. He is buried in suburban San Francisco.
Thomas McGeough's mother was Catherine Duffy, who was born and baptized in Inniskeen, County Monaghan, in 1857. Among her elder siblings (and I have names of a few) was my great grandfather James, born in August 1843, also in Inniskeen. They were baptized at the Roman Catholic Parish of Inniskeen. That building is still standing -- but it is now serving as the site of the Patrick Kavanagh Centre -- commemorating the life of the outstanding Irish poet of that name, who came from Inniskeen. (The church parish itself has a new home). The baptismal font used for the baptism of Thomas McGeough's mother, and of my great grandfather, is still located in the Patrick Kavanagh Centre.
Catherine Duffy -- after her marriage to McGeough resided of course in Dundalk. Her father -- who was also James Duffy -- died in 1880. For decades they had farmed a six acre property (leased to them) in Lacklom, a townland in Inniskeen. Somehow the property remained in the Duffy family until the early 1900's. But following her husband's death, Catherine (the mother -- nee Cook) - moved with her daughter Catherine Duffy McGeough to Dundalk. She lived until she was 99 years old -- dying in Dundalk at the home of her daughter Catherine McGeough Matthews (a younger sister of Thomas) in Dundalk. The year of her death was 1956. When I visited Innisken last summer, the farmer who currently owns the 6 acre property showed me where the Duffys lived (the house is no longer standing) -- and he called the field "Kitty Cook's field." He had no idea why it was called that. But I did -- it was the maiden name of your Thomas's grandmother Catherine Cook Duffy!
I believe I have successfully attached a photo below of James Duffy (the younger) - the brother of your Thomas's mother Catherine. This photo was taken in about 1880. He had come to America in 1869. He died in 1905 -- His wife and he had twelve children -- of whom only five survived into adulthood. Their children and I are in contact.
There is much more -- but perhaps this is a good beginning? I do not want to overwhelm you with data. If you wish to visit Dundalk, I can give you a couple pointers (it is a delightful city to tour). The train station alone is worth the visit. It was built in the 1860's -- it has been beautifully restored. Obviously our ancestors had to have used it often. Dundalk is easily reached by train from either Belfast or Dublin.
Ed