maybe somewhere way back in Ireland.
If you take a look at the last link I gave, in the following sentence it also says that Leahy has also done some genealogy, so he would know if there was a relationship. So, you could probably contact him for a better answer.
Senator Leahy put up the committee discussion of TWO US CITIZEN PARENTS in vetting McCain again after it was gone for a while - http://www.leahy.senate.gov/press/the-introduction-of-a-senate-resolution . Now, why of all the bills he’s proposed, did he pick this particular on to place under his explaination. Just makes ya go hmmmmm.