Does the husband’s son inherit from the wife of his father?
See the answer to question no. 147802
If she has died and she had saved up some of this pension, then this money and whatever else she left behind becomes the right of her heirs who survived her, and the heirs of her husband have no right to any of it.
The husband’s son does not inherit anything from the wife of his father, so he has no right to this money unless his father’s wife bequeathed something to him.