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I worked on the McGarvey family and will have to get back to you regarding the Greer family. The McGarvey lived in Glenalla townland in Aughnish civil parish. I did not find a marriage record.
Civil registration of births started in 1864. I located five children of Peter McGarvey and Sophia Griffin--- William 1864 (3rd link below) Fanny 1866 Daniel 1869 Catherine 1871 Sophia 1873 I did not find a record for Patrick. He may have been born before 1864 or if he was born after Sophia then maybe the birth was not registered. Can you check your records.
I did find the 1883 death record for Sophia the mother and a likely 1894 death record for Peter. The third link as indicated is the civil birth record for William.