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).
Note 4 - Microfilms of parish church rcds are kept by the National Library of Ireland (NLI).
For Dom(minic) McGlynn B 1867 +/- 4 yr, Boyle RC parish, Co. Roscommon, with the father's forename unknown, I found 2 rcds, both 1864, 1-civil rcd has a father forenamed Peter, the church rcd has a father forenamed Peter as well; these are likely duplicates for the same event.
For Peter McGlynn B ???? ditto, Boyle RC parish, with a father forenamed Peter, I found 1 rcd in 1876.
For Sarah McGlynn B ditto, I found 1 rcd in 1883.
For Mary McGlynn B ditto, I found 1 rcd, 1866.
Note - because of the range of ages, there are likely LOTS of siblings Brigid 1869, Dominic 1864, and Winifred 1870 are possibles.
For Peter McGlynn M 1862 +/- 4 yrs, Boyle RC parish, Co. Roscommon, I found 1 rcd, 1863. A view of the detailed rcd SHOULD show the bride's name and both Peter and Sarah's parents' names. This info will help identify and validate earlier generations B/M rcds.
For Peter McGlynn B 1837 +/- 4 yrs, Co. Roscommon, I found 1 rcd, 1839, Kilronan RC parish. There is 1 earlier B rcd in 1826, Boyle RC parish which MIGHT be the right one. Father's respective forenames were John and Dominic.
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.