Google does not seem to be my friend today or I am not asking it the right question.  Does anyone know how heirship laws in Pennsylvania work specifically toward mineral rights.  The below example is what I am trying to figure out:

(We are assuming that Great Grandpa Jones (GGJ) was the first to reserve the oil and gas rights to this particular 100 acres)

Great Grandpa Jones had 100 acres in Pennsylvania.  He sold the surface land but reserved all of the oil and gas rights.  Per the will, these rights were then passed down in equal shares to his 10 children (so 10 each), however, 1 of his children had passed and he specifically left the deceased child's portion of the acreage to the deceased child's 7 children.   Of these 7 children only 2 had children and none of the others had spouses.  We will call the 2 that had children Joe and Nancy.  Joe (who had 3 children) was the first to pass away and he had a will leaving his portion of the rights to his children.  The other 5 (child-less and spouse-less) passed away with no wills.  Would their shares go directly to Nancy (the sister) or be split between the daughter of Joe and Nancy?

Any info or a link would be greatly appreciated.

Thanks!