if a woman wants to go for hujj will her father-in-law be her mehrum, if her husband is not going with her or should she go with her husband only?
In principle, a father-in-law is a Mahram. It is prohibited for him to marry his daughter-in-law just as it is prohibited to marry one’s daughter or sister.
A woman can travel with her Mahram. That also includes the father-in-law. However, there is no doubt that there is a difference between a daughter and daughter-in-law. A man could be attracted to his daughter-in-law. That is not so much in the case of a daughter. It is, therefore, advisable that precaution be taken and the daughter-in-law do not travel alone with the father-in-law.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai