My research on the Mark McHugh line is that Mark was born about 1804 and died Aug 15, 1894 in Chancery. I believe he was part of the McHughs in Carrowkeel, prevalent on the 1857 Griffiths Valuation for that townland, possibly a brother/cousin to James, Daniel, Patrick, William, and Peter.
He married Margaret Carney, who died Dec 28, 1903 in Chancery, age 90. Their son Michael, who married Mary Gibbons, applied for a pension under the Old Age Pensions Act of 1908. Proof of age was a requirement (
http://censussearchforms.nationalarchives.ie/search/cs/home.jsp), so a search of the 1841/1851 censuses (since destroyed) was done. However, the results of the search were filmed and the image is available online. Michael's parents were listed as Mark McHugh and Margaret Canny (spelling or transcription error). Since Michael had not yet been born the notation is that he was not listed on sheet 5 of the 1851 census. Unfortunately, unlike searches completed for others who listed Toormore, the researcher did not jot down the names of the family members who really were on the 1851 census.
Mark appears on Griffiths Valuation of 1857 as a landholder in Toormore East - adjacent to John Kearney and Patrick Kearney. He also appears on the Landed Estates Court Rentals images as a tenant there in 1855 and again in 1878, when these lands were put up for auction. He has 1 mention in the 1882 Petty Sessions register just for good measure.
I have found a marriage record for Mary McHugh, Currabrone (Toomore), daughter of Mark McHugh to Patrick Groark in 1871 in Keelogues, with 3 children following, Michael, Anne, Margaret. Patrick died in 1877. Annie appears on the 1901 census as Michael McHugh's niece, residing with his family.
My own interest is in my gggrandmother Catherine McHugh, who married Thomas Rowland, of Gort, Ross, Castlebar in 1876. The Keelogues parish register seems to have a badly written/misspelled record which was unfortunately not recorded with civil authorities so I cannot verify her parentage. Sigh. But, there is a baptism registered Nov 10 1848 in Keelogues for Catherine, daughter of Mark McHugh and Margret, with William McHugh and Maria Carney, sponsors. I think they are one and the same person. And, Kate has a number of legal issues outlined in the Petty Sessions registers, including a stint in jail at one point. Feisty.