Thanks, Tim, for the baptism records. I'll have a close look to see if there is a Bernard amongst them, which could indicate a connection. But a bit difficult because there is at least one generation's gap.
The particular family I'm interest in had left Ireland by 1855. Mary & Alice to Australia 1850, mother Mary and Ann to Australia, 1855 - father Bernard alive in 1849 but deceased by 1855. I assume that Thomas must have gone to US prior to his mother's departure, otherwise I'm pretty sure he would have come to Australia instead. (Mother Mary proceeded to bring out all the adult children of her deceased sister, Ann, and managed to reunite almost all the family in Australia.)