Firstly, the principle is that once a man consummates marriage with a mother, her daughter (his stepdaughter) becomes permanently forbidden for him to marry. Also, consummating marriage with a daughter prohibits marrying her mother permanently, as stated in the Qur᾽ān: “And [also prohibited to you are] your stepdaughters under your guardianship born of your wives with whom you have consummated the marriage.” [An-Nisā᾽ 4:23] So, the prohibition of marrying the daughter requires the consummation of marriage with her mother, not just the contract alone.

So, if he consummates marriage with the mother under a valid contract, the daughter becomes forbidden to marry [her stepfather] permanently. In fact, the majority view among the Ḥanafīs and Ḥanbalīs, and a view from the Mālikī school, is that the daughter becomes forbidden to marry [her stepfather] permanently if the mother has engaged in unlawful intercourse (zinā), contrary to the Shāfi῾īs who require consummating marriage with the mother under a valid marriage contract.

Secondly, the principle regarding clothing and seclusion with non-marriageable kin is to prevent temptation. So, mere kinship alone is not sufficient; there must be prevention of temptation. The same applies to all interactions among non-marriageable kin, such as traveling together, living in the same place, uncovering lawful private parts, and so forth, where prevention of temptation is necessary. If temptation is prevented, then treating them like marriageable kin is permissible; otherwise, it is not.

Thirdly, the unmarriageable women are not all of the same level in terms of interactions with non-marriageable kin. For example, the mother is unmarriageable, but she is protected by both religious law and natural inclination. Thus, no matter how much she uncovers or loosen her clothing or lives with her son in the same room, she is still protected and secure. The same applies to the sister, and it extends to maternal aunts and paternal aunts.

However, the situation is different with, for example, the wife’s sister. Although she is unmarriageable upon the marriage of her sister and her sister’s husband, she cannot uncover herself in front of her sister’s husband as she would with her own brother, due to the difference in the level of kinship. Similarly, the stepdaughter, the daughter of the wife, falls under the category of “maḥram” through affinity and not blood relationship, so the consideration is different.

We recommend caution regarding the teenage stepdaughter; she should not loosen her clothing in the presence of her mother’s husband (her stepfather) as she would in the presence of her own father or brother, however, she is not obliged to wear a ḥijāh in front of him. Likewise, she should not seclude herself with her mother’s husband in the house unless both of them feel safe from temptation, or there is another impediment, such as the old age or illness of the mother’s husband, or the presence of his daughters in the house. Otherwise, caution is highly recommended.

Fatwa issued by Dr. Khālid Naṣr