Kieran,
Thank you for your quick and informative reply. You've been a great help! My great grandparents were Peter Regan and Catherine Shannon. I believe they were married in Fermoy in 1862 before leaving for New York. Peter's siblings Elizabeth, Hannah, and Bartholomew joined them, probably at a later date. They would have left Peter's aforementioned parents, William Regan and Margaret (Kearney), behind. I have no knowledge of any other relatives that stayed so the O'Regans you mention unfortunately don't ring that bell with me.
I'll probably visit Kilkrumper Cemetery but, thanks to your recommendation, I won't spend time searching for something I won't find. Our visit to Ireland has been loads of fun and I have been blessed with the guidance of wonderful people like yourself.
We'll be stopping off in Fermoy for a little while tomorrow, as I write this, so I don't expect that we could meet. Nevertheless, I hope we can meet at some point and welcome any tips you may have. My email address is jjleddy@mac.com.
I'll be traveling with a friend for the next two weeks hiking the Wild Atlantic Way and searching our respective genealogical trails. Thank you and everyone at Ireland xo for your help and attention.
John Leddy