Who are the people before whom a Muslim woman may remove her hijab?

A woman's mahram are those whom she is forbidden to marry permanently, and before whom she is permitted to remove her hijab.

There are three categories of mahram: 1. Mahram by blood relation (nasab): These are the ones mentioned in Surat An-Nur (fathers, sons, brothers, sons of brothers, sons of sisters), to whom paternal uncles and maternal uncles are added. 2. Mahram by fosterage (rada'a): Anyone forbidden by blood relation is also forbidden by fosterage, as the Prophet, peace and blessings be upon him, said: "What is forbidden by blood relation is also forbidden by fosterage." 3. Mahram by affinity (musaharah): These are those whose marriage is permanently forbidden due to marriage, such as the fathers of husbands and the sons of husbands.