If they are going to use the grandchild as a replacement for their son, then it is extremely selfish and putting unfair pressure on a child that never asked to be born, and especially under those circumstances. I mean, I am assuming that they are going to attempt to raise the child themselves, so what is going to happen when the child questions them on their parents? I mean what are they going to say? It would in all likelihood leave the child horribly confused and resentful, especially if they construe their grandparents percieved "good intention" as a selfish gesture in carrying on a bloodline. That is assuming the grandparents are going to even be around when the child reaches an age where they can question their parentage, because if they are pushing on in their years then they may be dead before the child reaches puberty and what then? An orphanage? Social services? They may be doing this out of love and grief for their son, but it descends into selfishness if it stands to ruin anothers life.