Decided to look into the Thomas Miggin who married Catherine Reilly in 1877 since he had a deceased father James...
This must be that Thomas:
http://www.census.nationalarchives.ie/pages/1901/Meath/Kildalkey/Ballaghtalion/1620725/Born in approximately 1841.
Son in the census was born in about 1880.
Looked up James Miggin born in 1880, and exact in that year was a James born to Thomas Miggins and Catherine Reilly. As far as I can tell, that's the only child they had.
Tried to find a death record for Catherine Miggin who may have been Catherine Reilly who died between 1880 and 1901 and came across this:
https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1899/05806/4643560.pdf -- the informant was a Kate Reilly. I haven't looked through all the records yet, but this one I will hold onto just in case.
Does this tell me who may have been the father of the Thomas Miggin and/or Owen who had a deceased James Miggin father? Nope! That would make things too easy.
In looking through Roots Ireland, for Thomas Miggin born in 1841 +/- 5 years, there's 3:
-- in 1841, born to Thomas Miggin and Mary Cusack (Ballivor)
-- in 1843, born to John Miggin and Margaret Walsh (Trim)
-- in 1844, born to Christopher Miggin and Catherine Gafney (Ballivor)
Sigh.
And I don't see *any* Thomas born to James Miggin and Alice Reynolds.