Answer
Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- Marrying stepmother’s daughter is permissible and we have witnessed many examples of this marriage. In this case, the man is not marrying his sister as the girl is not his full sister or even half-sister from paternal or maternal sides.
2- The daughter from his step mother (i.e. born to her from a previous husband) is not linked to the man in question either through blood or fosterage. This marriage is valid and correct as it does not involve any legal reason for the prohibition of marriage.
In his response to the question in point, Dr. Muzzammil H. Siddiqi, former President of the Islamic Society of North America, states:
Yes, it is permissible for a man to marry his stepmother’s daughter, if this daughter was born to her from a previous husband, because there is no kinship between these two young people.
This young man is not a mahram (unmarriageable) to that young girl. Allah mentioned in the Quran the women who are forbidden for marriage and then He said, {Lawful unto you are all beyond those mentioned, so that you seek them with your wealth in honest wedlock…} (An-Nisa’ 4:24)
Allah Almighty knows best.
Editor’s note: This fatwa is from Ask the Scholar’s archive and was originally published at an earlier date.