Answered by Ustadh Salman Younas
Question: Can a non-mehram man do hajj-e-badal for a woman when her sons are alive?
Answer: assalamu `alaykum
It would be valid for a non-mahram man to perform Hajj on behalf of a woman. [Ibn `Abidin, Radd al-Muhtar]
This is because the main consideration for validity when appointing someone to perform Hajj on one’s behalf is that such a person be legally suitable for the performance of the Hajj rituals. This condition excludes, for example, appointing someone who is not considered morally responsible. [ibid]
It is best to appoint someone who has knowledge of the rituals of Hajj and who is not obligated to perform Hajj him or herself. Rather, for someone to perform a Hajj on behalf of another while they themselves are obligated to perform it is prohibitively disliked. [Ibn Humam, Fath al-Qadir; Ibn `Abidin, Radd al-Muhtar]
Lastly, as the rules relating to appointing another to perform Hajj on one’s behalf constitute a number of details, it is highly advised that one consult a reliable scholar on these details before going ahead with things.
Checked & Approved by Faraz Rabbani