ANSWER:

No, this is not permissible as her brother in law is not her mahram and the prophet salla Allahu alaihi wa sallam prohibited for a Muslim woman to travel without a male mahram of her own, even for hajj. 

Sheikh I want to ask that my mother wants to go to hajj with her sister and brother-in-law Age of my mother is 62 years, her sister’s age is 60 years and her brother in law’s age is 65 years And the brother in law already performed hajj twice So is this permissible for her to go with these two

Hajj and Umrah, Mahram |