Is the husband of the grandmother considered a mahram to the daughter and the granddaughter?

The stepdaughters (Raba'ib) of a wife are forbidden to the mother's husband once the marriage contract with the mother is concluded and consummation has occurred, whether or not they are under his guardianship. This is a consensus among scholars, who cite the verse: "And your stepdaughters who are under your guardianship (Raba'ibukum allati fi hujurikum)" [An-Nisa 4:23]. They are of the opinion that the phrase "under your guardianship" has no [restrictive] meaning. However, if a man divorces the mother or she dies before consummation, he is permitted to marry her daughter, based on the verse: "from your women with whom you have consummated marriage. But if you have not consummated marriage with them, then there is no blame upon you [in marrying their daughters]" [An-Nisa 4:23].