Michael A. Cronin born 1821

Hello!  I'm looking for information on my great great grandfather, Michael A. (Andrew, Alexander, Aloyisius, maybe?) born in Ireland 1821 (maybe a year or two off;  not sure of birthdate but may be January) and don't know where (lots of Cronins in County Cork but that doesn't make him from there.) 

By the mid-1850s he was in the state of Georgia in the United States.  He married Agatha Bostick there, she passed away young, then he remarried.  His second wife was Martha Weathers McNeal Cronin born in Georgia, she was a widow with two sons.  Michael and Martha had several children (Dicey Emma, Catherine, Sarah Elizabeth, and John Thomas) in Georgia, then after the American Civil War, around 1866-67, they moved to Alabama where another son, Joseph, and my great grandfather Jasper N., was born.  

Michael died in January 1877 in Alabama. 

Family lore says he came to America with two brothers into the Port of New York.  One brother went to/stayed in Brookline (Massachusetts?), one to Minneapolis-St. Paul (Minnesota) and Michael went south to Georgia.  This was told to me by an elderly cousin who may have fallen prey to the "there were three brothers, went went north, one went west, and one went south....story....so not putting a lot of faith in that, still looking, but not finding immigration of a Michael born around 1821 arriving in New York with two brothers.

I can't find anything here in the USA that shows where he came from, only Ireland.  He was naturalized here sometime before 1870 as it shows on that census (first time question was asked) that he reports being a naturalized citizen. 

He was a school teacher in Georgia and Alabama, literate, beautiful handwriting, so was educated.  He and his family here in America were Methodist.  I don't know if he was a member of another church before he married Methodist Martha.  

I would love to find his Irish roots and family!  Thank you!!