Shanahan / Halloran /Casey?

Hi - I'm a descendant of Denis Halloran and Margaret Shanahan who lived in Ardrahan in 1901/1911.  I see that a John Shanahan in Ardrahin on the Griffiths valuation, who I believe would be my gg grandfather.  I think I'm also somehow related to O'Briens, including the late Josie O'Brien who married my great uncle James O'Halloran late in his life.  But she was already a cousin.

I'm curious where my g-grandfather Denis may have come from.  There are some Hallorans in Ballylanders in Griffiths' valuation.

Several of Denis and Margaret's children went to the US and settled in New Haven CT, later on several moved to New York City - David, Bridget, and James.  I was told that James was sent to the US by his family, something to do with his knowledge of the train rescue.  

I think Mary Ann went back, and I'm not sure about Catherine.

Denis, my grandfather, married a Hannah Casey in New Haven, both of her parents were Casey's, .  She went by Annie. I have hit a complete dead-end trying to find her records of where she came from.  I know there was a priest in the family (in the US), on that side, and my father told me stories about one of them being paid a pension on the condition that he not return. 

I have also been told that my grandfather Denis returned to Ireland twice, once to settle his father's estate, and again in 1922 to join the civil war.  I can find a record of the first visit, but not the second.

Anyway, I have fond memories of my grandfather and how every St. Patick's day someone in Ireland sent him shamrocks.

I hope to visit soon

Joan