Under Pennsylvania law, who can the heirs of a deceased sibling inherit money from the sale of real estate from a deceased parent?

Hunh?  Let me make sure I understand.  There is real estate.  Owner is deceased.  Survived by no spouse, only children.  Any children who were alive when the owner passed away would have been intestate beneficiaries of the Owner's estate.  Any child who predeceased the owner would have no share of the estate.  Assuming that a child died after owner died.  That deceased child's estate would be entitled to his/her interest in owner's estate.  That share would pass according to deceased child's will or intestacy if no will.  Confusing enough?