Answer: For a woman, her mahram is anyone who is connected to her by blood or fosterage and is permanently unlawful for her to marry. As such, the father, grandfather, brother, son, grandson, maternal and paternal uncles, nephews are all considered to be mahram to a woman. The husband is a mahram on account of marriage. Those who are mahram to the woman will be allowed to see her without hijab. Similarly, they will also be allowed to see her without the purdah if she wears it.

And Allah knows best.
Mufti Waseem Khan