My great grandfather was born in or around Rome before immigrating to the US as an adult. However I believe he may have Irish ancestry, based upon my DNA results and a lack of any matches from around Rome.
My irish matches (all 4th cousin matches and many more distant) don't match or share any matches with any of my mothers close or distant cousin matches, nor any of my fathers paternal cousin matches or his maternal grandmothers matches, and my paper trail shows no irish ancestry anywhere. I've therefore determined by process of elimination that Irish DNA matches I have match on the side where my Roman ancestry should be. Many of these irish matches share a surname Caldwell as well. I also have a small amount of unexplaned English/irish dna.
So my question is, what is the liklihood that in the 1700 or 1800s someone from Ireland would immigrate to live in Rome, Italy? My thoughts are either my great grandfather wasn't really my great grandfather or someone, likely with surname Caldwell immigrated to the Rome area in the 17 or 1800s and married into the Abbo family.