Barney Fox/John Fox

Hi all,  we have an ancestor that none of us can find.  John Fox.  Don't know any dates or locations.  However, do know his sons and wife.

Wife: Mary Flynn, born about 1801, died in Portland Maine, USA, Feb 1853 

She had arrived in Maine in 1847 from St. John, New Brunswick, Canada in 1847.  I can't find the record of when or where she left for Canada or landed in Canada.  However, her documentation says that she was born in Ireland.  There is no record that John Fox ever arrived in the US.  

There is a thought that the family came to the US, went to Canada and then she and the boys came back from Canada.  However, I have no proof of that.

Their sons, John, B 1823, MIchael b. 1831, William b. 1834, Barney b 1839, Martin b. 1841, and possible James, b. 1844 have records that indicate they were born in Ireland.  Barney's records indicate Leitrim, Galway, Ireland.  I don't know which Leitrim.  I've concentrated on trying to find Barney because he has the most unusual name, and he is my great grandfather.  Someone gave him the name of Barnabus, but I only see that once.

Several other researchers in my family have looked for John's information, with no results.  Where else should I look?

Thank you for any assistance that you can provide,

Theresa Foxx-Wishert ,