Reading all the research work you've done was fascinating. In addition to the fact that I was told the Brosnahans were related, that my grandfather's brother Jeremiah went to Australia when the boys emigrated, etc. my father and his back generations used the French spelling of "Denis", and the family came originally from a small town very near Killarney: so I thought I would suggest you continue your searches there in Rathmore. I was there in 1972 and it seemed nearly everyone in the town was named Moynihan! Aunt Julia Mary (who stayed in Rathmore) was a Moynihan who married a Moynihan and her son Denis married Eileen Kelly ( here in the USA her nephew Denis married Mary Kelly). A similar situation developed here when my father's mother Mary Collins from Cork died at age 29 - her husband Denis Moynihan married Margaret Moynihan from Massachusetts - so the genealogy is very convoluted and layered. Good luck.