The Stepdaughter is Prohibited in Marriage Even if She was Not Under the Guardianship of Her Stepfather
Allah subhanahu wa ta’ala said,
وَرَبَائِبُكُمُ اللَّـتِى فِى حُجُورِكُمْ“…your stepdaughters under your guardianship,”
The majority of scholars state that the stepdaughter is prohibited in marriage for her stepfather (who consummated his marriage to her mother) whether she was under his guardianship or not.
The Two Sahih recorded that Umm Habibah said, “O Messenger of Allah! Marry my sister, the daughter of Abu Sufyan (and in one narration `Azzah bint Abu Sufyan).” He said, “Do you like that I do that?” She said, “I would not give you up for anything, but the best of whom I like to share with me in that which is righteously good, is my sister.” He said, “That is not allowed for me.” She said, “We were told that you want to marry the daughter of Abu Salamah.” He asked, “The daughter of Umm Salamah” She said, “Yes.” He said, “Even if she was not my stepdaughter and under my guardianship, she is still not allowed for me because she is my niece from suckling, for Thuwaybah suckled me and Abu Salamah. Therefore, do not offer me to marry your daughters or sisters.” In another narration from Al-Bukhari, “Had I not married Umm Salamah, her daughter would not have been allowed for me anyway.” Consequently, the Messenger stated that his marriage to Umm Salamah was the real reason behind that prohibition.
Prohibiting the Daughter-in-Law for Marriage
Allah subhanahu wa ta’ala said,
وَحَلَـئِلُ أَبْنَآئِكُمُ الَّذِينَ مِنْ أَصْلَـبِكُمْ
“The wives of your sons who (spring) from your own loins,”
Therefore, you are prohibited to marry the wives of your own sons, but not the wives of your adopted sons, as adoption was common practice in Jahiliyyah. Allah subhanahu wa ta’ala said in Surah al-Ahzaab Ayah 37,
فَلَمَّا قَضَى زَيْدٌ مِّنْهَا وَطَراً زَوَّجْنَـكَهَا لِكَىْ لاَ يَكُونَ عَلَى الْمُؤْمِنِينَ حَرَجٌ فِى أَزْوَاجِ أَدْعِيَآئِهِمْ
“So when Zayd had accomplished his desire from her (i.e. divorced her), We gave her to you in marriage, so that (in future) there may be no difficulty to the believers in respect of (the marriage of) the wives of their adopted sons when the latter have no desire to keep them (i.e. they had divorced them).”
Ibn Jurayj said, “I asked `Ata’ about Allah’s statement, وَحَلَـئِلُ أَبْنَآئِكُمُ الَّذِينَ مِنْ أَصْلَـبِكُمْHe said, `We were told that when the Prophet married the ex-wife of Zayd (who was the Prophet’s adopted son before Islam prohibited this practice), the idolators in Makkah criticized him. Allah sent down the Ayat: وَحَلَـئِلُ أَبْنَآئِكُمُ الَّذِينَ مِنْ أَصْلَـبِكُم and Surah al-Ahzaab Ayah 4 وَمَا جَعَلَ أَدْعِيَآءَكُمْ أَبْنَآءَكُمْ “nor has He made your adopted sons your real sons.” And Surah Al-Ahzaab Ayah 40, مَّا كَانَ مُحَمَّدٌ أَبَآ أَحَدٍ مّن رِّجَالِكُمْ “Muhammad is not the father of any of your men.”
وَأَن تَجْمَعُواْ بَيْنَ الاٍّخْتَيْنِ إَلاَّ مَا قَدْ سَلَفَ“…and two sisters in wedlock at the same time, except for what has already passed;”
The Ayah commands: you are prohibited to take two sisters as rival wives, or rival female-servants, except for what had happened to you during the time of Jahiliyyah, which We have forgiven and erased. Therefore, no one is allowed to take or keep two sisters as rival wives, according to the consensus of the scholars of the Companions, their followers, and the Imams of old and present. They all stated that taking two sisters as rival wives is prohibited, and that whoever embraces Islam while married to two sisters at the same time is given the choice to keep one of them and divorce the other.
Imam Ahmad recorded that Ad-Dahhak bin Fayruz said that his father said, “I embraced Islam while married to two sisters at the same time and the Prophet commanded me to divorce one of them.”