Is it permissible for my non-Muslim brother to be a mahram for me during travel?

The Prophet Muhammad, peace be upon him, forbade a woman from traveling without a mahram. A mahram is her husband, or anyone to whom she is permanently forbidden in marriage due to lineage, suckling, or marriage affinity.

If the mahram is a disbeliever, a Muslim woman is not permitted to travel with him or be alone with him if he is of deviant character. However, if he is trustworthy, most scholars have allowed traveling with him. This is the view chosen by Sheikh Ibn Uthaymeen, on the condition that she is safe with him. The Hanbalis, however, disagreed with this, holding that a disbeliever cannot be a mahram for a Muslim woman.