All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, you should know that dividing the inheritance correctly requires determining the heirs correctly; the heirs (who are entitled to inherit according to Sharee’ah) among the men exceed ten, and among the women they are eleven, so it might be that there is an heir whom you did not mention because you think he is not entitled to inherit.
Hence, our answer to you is based on the assumption that there is no heir except those mentioned in the question. So, if your grandfather left behind no heir except his wife and his two sons, and then his wife died and left behind no heir except her two sons, then the inheritance of the grandfather should be divided between his two sons directly as if he died and did not leave a wife. In which case, his inheritance should be divided into two shares: one share for each son.
As regards the share of your father, it should be divided amongst his heirs. However, you did not mention to us who are his heirs so that we can clarify how his inheritance should be divided.
Allaah Knows best.