Well 'cause of the large families in those days, most were related, some changed their surname to Byrne.
In the regions of BALLINAMEEN, CROGHAN, a lot of the deceased were buried in Croghan during that era , it is appx. 2.5 mls apart.
Boyle is appx. 8.0 miles from Ballinameen, so from this information, you may understand where relationships developed, or close family ties.
Does your family tree show a Farrell and a Maggie as his siblings ?.Of course there could be many more, that region had a lot of families emigrate to the USA, including my own.
My brother has done his dna , may not be of great value just yet, but will certainly be of use in the not too distant future.
Do you have any pictures of the older generation, the O'Beirnes mostly had high cheek bones, and still do today.
Looking forward to hearing from you.