Q. Can my sister’s grandson or my husband’s nephew travel as my Mahram with me for Umrah?
A. Your brother’s or sister’s grandsons are considered to be your Mahrams. However, your husband’s nephew is considered to be your non-Mahram (stranger).
Therefore, it would be permissible for you to travel for Umrah with your sister’s grandson as your Mahram but it would not be permissible for you to travel with your husband’s nephew. (Ahsanul Fataawa 5/91)
Allah Ta’ala Knows Best
Mufti Ismaeel Bassa