What is the ruling on a Muslim woman traveling with her non-Muslim sister and the sister's son in a private car for seven hours to visit their brother, who is ill with what is likely a terminal illness?

The majority of jurists agree that there is no distinction between a Muslim and a non-Muslim regarding the mahram (definition) with whom a woman is permitted to travel. Ahmad, however, dissented on this point. The preponderant opinion is that of the majority. Consequently, if the woman's nephew (sister's son) is an adult, he is a mahram to her, and she is permitted to travel with him with the permission of her husband, if she has one. Al-Sarakhsi mentioned that a mahram can be a free person or enslaved, Muslim or non-Muslim, as long as he is not a Magian, in which case travel with him is not permissible. Al-Hafiz defined a mahram as someone whom it is perpetually unlawful for a woman to marry due to a permissible reason related to her sanctity. Ahmad exceptionally excluded a non-Muslim father from being a mahram for his Muslim daughter regarding travel, fearing temptation. Al-Shawkani extended this ruling to include other relatives, and Al-Ruhaibani Al-Hanbali mentioned that a Muslim woman should not travel with her non-Muslim father.