Greetings ! My Great Grandfather was Michael Higgins, brother of Bernard, married to Bridget Cruise. Their father lived at Cloonfineen, Roscommon and his sons included Patrick before 1839, Michael born 1840, Bernard and Thomas born 1847. Patrick married Margaret Connolly and lived at Cloonacalgy, Michael lived at Culkeen and Thomas at the original home at Cloonfineen and as you stated, Bernard at Pollynoon.
I see only one reference to Martin as father in the parish record of Kiltullagh and his wife is listed as Bridget Higgins which might explain why Bernard chose to remain in Galway as there were other Higgins families there beside the ones in Kiltullagh.
I have a record of a Catherine Higgins who married a Michael Connally [from the parish of Templetogher ] in 1846 and they lived at Cloonfineen as did Martin Higgins [born 1816 and died 1880 ]. Catherine could have been a sibling of either Martin or Bridget.
In my records I list the siblings of your great grandmother Nannie as Martin married to Mary Tully
Kathleen Higgins married to Frank Seamas [California]
William Higgins married to Amelia Cuttle
I wasn't aware of John
It is of course wonderful to find another cousin. I started my family research about 20 years ago and I do have messages out in cyberspace dating back to those days, some with email addresses long since become obsolete. That is why every so often I repost in a new place with hopes a relative will see the message and reply.
Looking forward to sharing info about our family tree
cousin Michael Duffy in NY, son of Eileen Higgins, grandson of Michael Higgins, great grandson of Michael Higgins and great great grandson of Martin Higgins.