Is there a reason why he'd be Protestant rather than Catholic? It's possible, but if his relatives are Irish, there's a better chance that they'd be Catholic. I suppose there's even a chance they could be Jewish, though that would be a MUCH, MUCH smaller chance than Protestant, but being Jewish depends on whether or not the mother is. (That was changed recently in Reform Judaism, but not anywhere else)I'm just guessing, but I don't think there have been too many Jewish women named "Mary" for the last 2000 years.