Legal Question in Wills and Trusts in Pennsylvania

Not in the US. You would have to talk to a lawyer in the place where ther property is located.

You post no relevant details. If the property is owned by grandfather, when did he die? Was it mother or father's father? Where did grandfather live at the time of his death? Did grandfather have a will? Was grandfather survived by a spouse?

Assuming grandfather did not have a will (my answer is premised largely on PA law) or spouse, grandfather's assets, all of them wherever they may be, would pass to the children of grandfather. You do not indicate who was grandfather's child here and if grandfather died before or after mother or father. The property may have then passed either as per a will, if grandfather had one, or if none, to his children, and if one of the children died before him, then directly to grandchildren. If to children who later died, then the share of the dead child goes as per the dead child's will or state intestacy laws.

If we are talking many years, there is no reason to open the estate for father for sure. Since mother died today, then an estate would be opened for her but its only relevant if she was a child of grandfather and grandfather died before her.

You are still going to need to talk to a probate attorney who practices in the country where the land is located and that attorney will need to look at grandfather's will if any and the intestacy laws to see where the property goes.