Males to whom a woman cannot be married, such as her father, brother, or uncle, who are allowed to be a woman's escort when traveling. Must be a close relative.
a man whom a woman may never marry because of the degree of closeness of the blood-relationship, i.e. father, brother, son, uncle, etc. A woman is not required to observe hijab in front of her mahram.
The husband, or a male companion of a female pilgrim to whom her marriage is expressly prohibited by the shariah (e.g., father, brother, uncle, nephew, etc.) A woman must be accompanied by a Mahram for Umra and Hajj.