Reginald J Barrett Born 1845 Ireland

I am hoping for some information on Reginald J Barrett who was born in Ireland in 1845. His father was Joseph Barrett born 1818 St Mawes in Cornwall. Joseph was a Master Mariner who obtained his certificate in Cork in 1851, which makes me think that he was living in the County.
Joseph also had a twin brother Thomas Barrett, also a Master Mariner, who may also have moved to Ireland