Hello Hughie, welcome to Ireland Reaching Out, I have found a number of siblings for the family on the civil registration of births which commenced in 1864, there are none prior in the church records that I can see but siblings up to 1885, busy people, church records for Ardee appear to be missing and the Register on the National Library site does not record any around that time, oddly they are there for the early 1800s. They lived in Cappocks Green in Ardee town. I have attached the records found.
No marriage record but obviously prior to 1864 probably 1863, this is a blow for now but hopefully they may turn up, I tried to look at Griffiths Valuation but the Ask About Ireland site is down all week end, these records are just head of house and land owned or rented but are useful as the maps show where the land was, in this case they appear to live just outside the town. The civil records show a death of a James McCoy in 1867, possibly a father and two other marriages in the area, one I remember was from Stickillen nearby, the mothers name is found in the area so not too unusual, McCoy would but is found in adjoining counties.
There is a site about Louth here that should interest you, http://jbhall.clahs.ie/ there is also a Louth Genealogy Facebook page, it is a private page, ask to join.
Civil records are here, not all link to an entry. All births up to about 1918, deaths to 1968 and marriages to 1941. https://civilrecords.irishgenealogy.ie/churchrecords/civil-search.jsp Church registers are here https://registers.nli.ie/parishes/0183 no searching function except date, month and year.
The location of Cappocks Green is here https://www.townlands.ie/louth/ardee/ardee/ardee-urban/cappocksgreen/