After extensive research of the Giffin/Griffin line, and thompson, I now am certain that Simon Giffin from Massachussets originally from Ireland, and his father Simon from Scotland was the father of Michael Griffin. I believe he came over to Ireland, met Catherine Fahy, had a relationship and got her pregnant. Then went back to America.
I have Thompsons and Fergusons also in my Tree. Which seem to match up with Simon Giffins family.