The Folans in ireland all seemed to originate in Co Galway, and they sigend official documents as O'Folan as far back as the 16th century.
Today they are still concentrated in Co Galway, mostly in the city and the Irish speaking gaeltacht where they use the Irish version O Cualain.
For some reason they adopted Foley when they went to America as they seemed to think it was more american or easier to spell for people who had not heard the name Folan before, as it is a relativly unusal name in Ireland.
But its interesting that your father in law's DNA shared characteristics with Foley. How close was it? Was it with mainly American Foley's or Irish Foley's do you know?