1. One’s mother, father, grandmother, grandfather, great-grand mother, great-grand father and so on.
2. Children of one’s mother or father (whether they are real brothers and sisters, or step-brothers and step-sisters). Similarly, the children of one’s parents’ children (i.e. nephews and nieces, whether they are from one’s real brother/sister or step-brother/ step-sister) etc.
3. The children of one’s grandmother/grandfather (i.e. real uncles/ real aunties or step uncles/step aunties). However, the children of one’s uncle and aunt are non-Maḥram.
(Fatāwā Razawiyyaĥ referenced, vol. 11, pp. 464)
Note: Amongst the abovementioned blood-relatives, it is Ḥarām for these men to marry these women and for these women to marry these men.
Question: Does a daughter-in-law have to observe veil with her father-in-law?
Answer: No, there is no ‘veil’ between them due to Muṣāĥarat. However, she can observe veil with him if she wants; in fact, it is safer for her to observe veil with him if she is young or there is a possibility of indecency, especially these days due to the chaotic state of our society. Reports about ‘issues’ between the daughter-in-law and the father-in-law are not uncommon nowadays. These issues are usually one-sided, i.e. caused by the father-in-law. When he finds himself alone with his daughter-in-law, he tries to satisfy his lust with her. For this reason, these days women should not have