Is the marriage of a woman who committed adultery with her sister's husband valid, after they reconciled and married, having both divorced their previous spouses, and her brother attended in place of her disapproving son, despite 15 years having passed since the marriage? And should her children be advised to sever ties or to maintain them?

If a woman commits adultery with her sister's husband, she has committed a grave evil, and adultery is one of the major sins. If her demand for divorce was instigated by him, then he is corrupting her, and instigation (takhbib) is forbidden. The son has more right to arrange his mother's marriage than the brother. If he refuses to arrange her marriage without a legitimate Shar'i reason, he is preventing her from marriage (adil), and then the more distant relative arranges her marriage. It is obligatory for children to maintain ties with their mother, even if she commits major sins.