Being accompanied by the son of the sister's daughter for Hajj

Hajj - Mahram

Question: Is a woman allowed to be accompanied by the son of her sister's daughter for Hajj? 

Answer: Yes, she is allowed to go for Hajj with this man as he is the son of his niece. And the children of the niece are Mahram. 

[English version of "Être accompagné dans hajj par so sœur so tifille so garçon" – Al Jamiat – Vol.1 No.14]