Is it permissible to marry the daughter of one’s father’s paternal uncle?
Question

                Is it permissible for my brother’s son to marry the daughter of my paternal uncle? The grandfather of my brother’s son and the father of the girl are full brothers, and I am married to her sister. Is the marriage of my brother’s son to my wife’s sister permissible according to Islamic teaching?
Praise be to Allah.
	Yes, it is permissible for your brother’s son to marry that 
	woman, because in fact she is also regarded as the daughter of a paternal 
	uncle for him as well, because his father’s paternal uncle is also a 
	paternal uncle to him and to his children after him. Allah, may He be 
	glorified and exalted, says (interpretation of the meaning):

	“O Prophet 
	(Muhammad (blessings and peace of Allah be upon him))! Verily, We have made 
	lawful to you your wives, to whom you have paid their Mahr (bridal money 
	given by the husband to his wife at the time of marriage), and those 
	(captives or slaves) whom your right hand possesses - whom Allah has given 
	to you, and the daughters of your ‘Amm (paternal uncles) and the daughters 
	of your ‘Ammah (paternal aunts) and the daughters of your Khaal (maternal 
	uncles) and the daughters of your Khaalah (maternal aunts)”

	[al-Ahzaab 33:50]. 

	Shaykh ‘Abd ar-Rahmaan as-Sa‘di (may Allah have mercy on him) 
	said: Similarly, one of the things that Prophet (blessings and peace of 
	Allah be upon him) has in common with the believers is the words: “and 
	the daughters of your ‘Amm (paternal uncles) and the daughters of your 
	‘Ammah (paternal aunts) and the daughters of your Khaal (maternal uncles) 
	and the daughters of your Khaalah (maternal aunts)”. 
	That includes paternal uncles and paternal aunts, and maternal uncles and 
	maternal aunts, whether close in degree or otherwise.

	End quote from Tayseer al-Kareem ar-Rahmaan fi Tafseer 
	Kalaam al- Mannaan (p. 669)

	For more information, please see the answers to questions no.
	34791 and 112320

	And Allah knows best.