Thanks for that.
That John was a widower on 1876 marriage to Mary Murphy and believe 1st marriage might have been to Mary Michael in 1853 (there was a daughter Sarah born 1865 Dullaghy and probably other children before registration).
From marriage of John and Mary (Murphy) there was also a son Hugh in 1878.
Samuel's birth is not only not in index, under his name at least, but GRONI apparently were unable to locate it searching 1873-1887.