Can a disbeliever be regarded as a mahram for his Muslim sister when travelling?
Question

                Is it permissible for my brother, who is not Muslim, to be my mahram for the purpose of travel? I have embraced Islam but all my siblings are non-Muslims.
Praise be to Allah.
	The Messenger (blessings and peace of Allah be upon him) 
		forbade women to travel without a mahram. He said: “No woman should 
		travel unless she has a mahram with her, and no man should enter upon 
		her unless she has a mahram with her.” A man said: O Messenger of Allah, 
		I want to go out with such-and-such a campaign, and my wife wants to go 
		for Hajj. He said: “Go for Hajj with her.”

	Narrated by al-Bukhaari (1862) and Muslim (1341).

	Who is a woman’s mahram?

	A woman’s mahrams, with whom it is permissible for her to 
	travel, are: her husband, or anyone who is permanently forbidden to marry 
	her due to ties of blood or some other valid reason.

	Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:

	Her mahram is her husband, i.e., the one who has done a valid 
	marriage contract with her, even if no intercourse has taken place and he 
	has not been alone with her.

	The words “or anyone who is permanently forbidden to marry 
	her” exclude anyone for whom she is temporarily prohibited, such as a woman 
	who is in ihram for Hajj or ‘umrah.

	“due to ties of blood” means due to kinship 
	

	“or some other valid reason”. Valid reasons may be divided 
	into two categories:

	1.    
	
	Breastfeeding

	2.    
	
	Ties through marriage

	With regard to ties through blood or kinship, the mahrams in 
	this category are: the father, son, brother, paternal uncle, brother’s son, 
	sister’s son, and maternal uncle. These seven are mahrams due to ties of 
	blood, and it is permanently forbidden for them to marry the woman.

	Mahrams through breastfeeding are the same as the mahrams 
	through blood ties. Those who are a woman’s mahrams through breastfeeding 
	are: her father through breastfeeding, her son through breastfeeding, her 
	brother through breastfeeding, her paternal uncle through breastfeeding, her 
	maternal uncle through breastfeeding, the son of her brother through 
	breastfeeding, and the son of her sister through breastfeeding. So there are 
	seven through breastfeeding and seven through ties of blood. That is 
	fourteen.

	Mahrams through ties through marriage are four: the father of 
	the woman’s husband, the son of the woman’s husband, the husband of the 
	woman’s mother, and the husband of the woman’s daughter. They are the 
	ascendants of her husband, namely his father and grandfathers, and his 
	descendants, namely his sons and the sons of his sons and daughters, no 
	matter how far the line of descent reaches. These mahrams also include the 
	husband of her mother and the husband of her daughter. But there are three 
	who become mahrams as soon as the marriage contract is done, namely the 
	father of the woman’s husband, the son of the woman’s husband and the 
	husband of the woman’s daughter. As for the husband of her mother, he does 
	not become a mahram unless he has consummated the marriage with her mother.

	End quote from ash-Sharh al-Mumti‘ (7/37-38)

	For more information, please see fatwa no. 
	5538

	If this mahram – such as her father or brother – is a 
	disbeliever, can she travel with him and be alone with him when she is a 
	Muslim?

	There are two scenarios:

	The first scenario is when this mahram who is a disbeliever 
	has dubious morals or follows some evil ideas or religion that permits 
	intimacy with mahrams. In that case, it is not permissible for a Muslim 
	woman to travel with him or be alone with him, because the fear of fitnah 
	from him is like the fear of a stranger, or even worse.

	Ibn Qudaamah (may Allah have mercy on him) said:

	It is not appropriate for there to be any difference of 
	opinion concerning a Magian, because he is not to be trusted with her and he 
	thinks that she is permissible for him.

	End quote from al-Mughni (5/34)

	We may add to the category of the Magian anyone who follows a 
	similar evil path of believing that it is permissible to be intimate with 
	mahrams.

	The second scenario is when he is trustworthy. Most of the 
	scholars were of the view – and this is the correct view – that he is a 
	mahram for her with regard to travel, so she may travel with him, because he 
	is to be trusted with her in this case.

	The Hanbalis disagreed concerning that and were of the view 
	that the disbeliever cannot be a mahram for a Muslim woman. See: al-Mughni 
	(5/34).

	Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) favoured 
	the view of the majority of scholars and said:

	If he is of a different religion, as in the case of a 
	disbelieving man and a Muslim woman, then he may be a mahram to a Muslim 
	woman, on condition that he can be trusted with her. If he cannot be trusted 
	with her, then he cannot be a mahram and she cannot be allowed to travel 
	with him. End quote.

	Ash-Sharh al-Mumti‘ 
	(7/41)