Based on the years you have given, the estimated date of Margaret McKernan's birth would most likely have been before 1835. I cannot find a Margaret McKernan in that time period, in my family.I have a Margaret McKernan b. 1859, a younger sister of my paternal grandfather, Charles.
Charles and Margaret's parents were Henry McKernan and Sarah McCaigue.Henry's death was in 1883, with the age given as 78, which would given him a birth year of 1805. Perhaps this Henry had a younger brother, who had another Margaret McKernan.I have no information on this Henry's siblings. But I do know there was another Henry, married to another Sarah(?) who are definitely buried in the Curfeightrin RC Cemetry at St. Patrick's of Ballyvoy.These two pre-date 1800, according to the headstones. So there were many McKernans in the Culfeightrin area.