A man was engaged to a woman and had an intimate relationship with her before marriage. During that period, he also had a relationship with her sister. After discovering the matter, the fiancée is asking about the Islamic ruling regarding her situation.

The action of this person with his wife's sister is a grave assault and a crime that indicates the weakness of his faith and his baseness, to the extent that even the people of the pre-Islamic era (Jahiliyyah) would disdain such an act. This action does not affect the marital bond of the wife, because what is unlawful does not render lawful things unlawful. To know the ruling on his relationship with the one he has contracted marriage with, you can refer to Fatwas No. 32692 and 33384.