The Ruling on the Woman's Relatives with Respect to the One Who Married Her

There is a man who has daughters of marriageable age. What is the ruling on his daughters meeting their grandfather’s wife (the wife of their father’s father), and is she considered a mahram (a relative one may not marry) for them?
Any man who marries a woman and has sexual intercourse with her, all of her descendants, whether daughters, sons, or daughters of daughters, are mahram (relatives one may not marry) to him. Take this as a rule.Meaning: If a man marries a woman and has sexual intercourse with her, all of her offspring are mahram (relatives one may not marry) to him.