Must a woman wear a headscarf in front of her grandson's wife's husband, her niece's husband, and her step-granddaughter's husband?

The husband of a granddaughter (daughter of one's son) is a mahram to his wife’s grandmothers (the original female ancestors of his wife), based on the Almighty’s saying: "And your wives’ mothers" (Quran 4:23). This includes the mothers of the wife and her grandmothers. As for the husband of a niece (daughter of one's brother), he is not a mahram to his wife's sisters, because the prohibition between them is temporary, due to the Prophet's (peace be upon him) prohibition of combining a woman with her paternal aunt or her maternal aunt in marriage. The husband of a husband's son's daughter is not a mahram because there is no text that prohibits him.