I research the Irish Family History Foundation's database. It contains 12,800,000 surviving rcds for abt 70% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800. Cos. Donegal and Derry were recently added to the database.
Note 1 - Without a KNOWN county, the chance of an ancestor's rcds NOT being in this database is AT LEAST 30%.
Note 2 - Only 1/2 of Co. Cork's rcds are in this database.
Note 3 - The RC church kept control over most parish rcds from Tipperary (north). These are ONLY available thru the Tipperary Family History Research center at a substantial fee (regardless of outcome).
For Rose McGonagle M 1916 +/- 4 yrs somewhere in Ireland, I found 2 rcds: 1912 Donegal, and 1918 Fermanagh (Enniskillen RD).
For Mic(hael) McShane M ditto, I found 3 rcds: 1914 Donegal, 1818 Donegal, and 1918 Fermanagh (Enniskillen RD). The Enniskillen rcds are highly likely to be for your ancestors. A view of the detailed rcds SHOULD show they married each other. If so, the view MAY show their parents' names as well as other info. This will help identify and validate their B rcds and their parents' M rcds.
For Rose McGonagle B 1895 +/- 4 yrs, somewhere in Ireland, with the father's forename unknown, I found 5 rcds: 1892 Donegal, 1894 Donegal, 1895 Tyrone, 1896 Donegal, and 1897 Donegal. Father's respective forenames were Robert, Pat(rick), Pat(rick), Pat(rick), and Pat(rick).
For Mic(hael) McShane B 1893 +/- 4 yrs, somewhere in Ireland with the father's forename unknown, I found 12 rcds: 1889 Donegal, 1890 Donegal, 2-1890 Louth, 1891 Derry, 1892 Derry, 2-1895 Armagh, 1896 Mayo, 1896 Donegal, 1896 Armagh, and 1897 Down. Father's respective forenames were Mic(hael), John, Mic(hael), John, John, Pat(rick), Tho(mas), Mic(hael), Hugh, "Con", Charles, and Mic(hael).
Will leave it to you to find the named siblings and their genealogical info.
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.
Hope this helps. Good luck.