If my name and my sister's isn't on a deed and my brother dies and the property goes into foreclosure,in Pennsylvania,can the mortgage company come after my sister and me?

The mortgage company will come after whomever has signed the mortgage documents. If you are on the mortgage then yes, they will come after you for the amount due even if your name is not on the deed, because you promised to pay when you signed the mortgage.

The mortgage company will come after whomever has signed the mortgage documents. If you are on the mortgage then yes, they will come after you for the amount due even if your name is not on the deed, because you promised to pay when you signed the mortage.

Fortunately, I signed for nothing,nor did my sister.

Then no worries, other than having to find another place to live if your brother (or his estate) is unable to keep up with the mortgage and the bank forecloses.