A: Under Pennsylvania law when there is no will, assuming that your mother was not married at the time of her death, the estate would be divided into equal shares - one share for each living child and one share for each deceased child who has living children or descendants. Each living child would receive a share. For the shares of deceased children, the children of the deceased children would equally divide the share of their deceased parent.
So for example, if each of the 2 deceased children had 3 children of their own, then each of those grandchildren of your mother would receive 1/15 of the estate - that is one-third of their deceased parent's one-fifth share.
Note that the division of shares of the estate is of what is left after payment of the debts, administration expenses and taxes due from the estate.