I agree with Marion about a second child with the same first name if the first child died young.
My first impulse was to go to the Nat'l Lib. of Ireland Catholic Church records, but they didn't have baptisms for those dates for the parish of Burrishoole in the Archdiocese of Tuam in County Mayo. The Family History Library, however Does have baptisms for those dates on microfilm. Since you have baptism dates, you may be able to get printouts for both.