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).
It appears all of the children were NOT born in Ireland, or in a part for which rcds haven't been transcribed.
For Eliza(beth) Harris B 1853 +/- 4 yrs, Co. Cork, I found 2 rcds: 1851 and 1852. Note 2 may apply here especially considering her husband was from Kerry.
For Pat(rick) Breen B 1849, Co. Kerry rcds aren't in the database yet. Suggest you wait until they are.
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.