I research the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800.
Note 1 - Without a KNOWN county, the chance of an ancestor's rcds NOT being in this database is AT LEAST 35%.
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 Pat(rick) Pew B 1790 (exact), Rathkenny parish, Co. Meath, with the father forenamed Francis, I found 1 rcd. This is HIGHLY likely to be for your ancestor. Rathkenny parish B rcds begin in 1784, marriage rcds in 1867. Therefore, you are unlikely to find rcds for any earlier ancestors, at least in this parish.
For Pat(rick) Pew M 1814 +/- 4 yrs in Co. Meath, I found 0 rcds.
For Francis Pew B 1814 (exact) in Co. Meath with a father forenamed Pat(rick), I found 1 rcd in Rathkenny parish.
For Mary Pew B 1819 ditto, I found ditto.
For John Pew B 1821 ditto, ditto.
For Mich(ael) Pew B 1823 ditto, ditto.
For Bri(dget) Pew B 1825 ditto, ditto.
For Marg(aret) Pew B 1820 +/- 4 yrs ditto, I found 0 rcds.
The above results are HIGHLY likely to be for your ancestors and match your info precisely. A view of these B rcds SHOULD reveal the mother's forename at least.
For POTENTIAL siblings to Patrick, I found an Elizabeth B 1814, George 1815, James 1788, John 1794, Joseph 1820, Mary 1809, Peter 1801, and Thomas 1822. All these were B to a father forenamed Francis in Rathkenny parish. You will have to view each detailed rcd to find the mother's name and validate/invalidate each one.
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.