Allens of Limerick

My great-great grandfather was James Allen.  He died in 1881 in Medway, Massachusetts. His death record lists his father as being Michael Allen and his mother as Jane Kennedy. His headstone states that he was 49 years of age and a Native of Limerick, Ireland.  His naturalization papers also states he was from Limerick  and that he was born in about 1836.  Oral family history is that James's father (first name uncertain, but I think Patrick while others think perhaps James) came to Ireland in about 1830 with his brother, both being in the British Army at that time. The story continues that James's father married in Limerick and stayed there as a school teacher in a private school while James's uncle returned to England.  There is a baptismal record in Baggotts Town with a James, son of Patrick Alleyne and Jane Kennedy, being baptised on Sept 18, 1829.  One family member speculates that James Allen may have been from Rathkeale.  Any additional information would be greatly appreciated.   Fran Small