What is the ruling on a grandson marrying his grandfather's second wife, and does the prohibition in the verse "And do not marry those [women] whom your fathers married, except what has already occurred..." include the wives of fathers and grandfathers absolutely?

It is not permissible for a son to marry his father's or grandfather's wife. The noble verse: "And do not marry those [women] whom your fathers married, except what has already occurred. Indeed, it was an immorality and hateful [to Allah ] and was a wicked way" (Quran 4:22) encompasses everyone who has fatherhood, and it prohibits sons from marrying their fathers' wives in honor of the father and out of righteousness towards him, which was prevalent in the pre-Islamic era (Jahiliyyah). The Prophet, peace and blessings be upon him, ordered the killing of a man who married his father's wife.