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 Robert Millar B 1907 +/- 4 yrs, Co. Antrim, with a father forenamed William, I found 2 rcds: 1903, and 1907.
For Norman Millar B ???? ditto, I found 0 rcds at any date.
For Isabell Millar B ???? ditto, I found 1 rcd, 1911, within a relevant range.
For Jack/John Millar B 1907 ditto, I found 0 rcds.
For Mary McAteer M 1906 +/- 4 yrs, Co. Antrim, I found 12 rcds.
For William Millar M ditto, I found 30 rcds - too many to easily summarize here.
For William Millar B 1881 (exact), Co. Antrim, with the father's forename unknown, I found 14 rcds - again too many.
For Mary McAteer B 1878 (exact) ditto, I found 11 rcds: 2-1874, 1875, 1876, 1878, 1879, and 3-1881.
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.