128 grandparents
My mom sent us this pic of her 4x great-grandfather that she retrieved over the weekend, from her aunt in Delaware who was holding it for her.
John Parson Blair
My 5x great-grandfather. We think of one grandparent having a zillion great grandkids, but if you do the math it also goes the other way. He is one of my 128 grandparents in that generation. 64 sets. If you do the permutation, I have 254 grandparents back to the late 1700s.