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I searched the subscription site Roots Ireland and did not find a record for William. The baptismal records for the RC parish (Creggs/Glinsk) do not start until 1831 whcih likely explains not finding William's record.
You may want to add William's story to our XO Chronicles site and possibly someone will see a connection. https://www.irelandxo.com/ireland-xo/history-and-genealogy/ancestor-data...
Have you considered DNA testing?