Is refusing to visit the brother who married a woman after her divorce from her husband—following a previous relationship that occurred during her first marriage—and boycotting his children because of this marriage, a legally sound position?

A man's agreement with a married woman to marry her after her divorce is called "Takhbeeb," which is the act of corrupting another man's wife against him. It is considered one of the major sins. Scholars have differed on the ruling regarding the marriage of the one who commits Takhbeeb to the woman he corrupted, with two opinions: The majority of scholars hold that the marriage is valid despite the prohibition of Takhbeeb, while the Malikis and some Hanbalis consider the marriage null and void as a punishment for the one who commits Takhbeeb. The fatwa issued is that the marriage is valid as long as it fulfills all the prescribed legal conditions.

As for shunning the one who commits Takhbeeb, it is religiously sanctioned based on the Almighty's saying: "You will not find a people who believe in Allah and the Last Day loving those who oppose Allah and His Messenger." This shunning includes disobedient believers and is not limited to disbelievers. The Companions and the early generations shunned those who disobeyed Allah, even if they were their relatives. However, if signs of sincere repentance and remorse appear from the one who committed Takhbeeb, or if shunning is not effective in reforming him, it is preferable to end the shunning. One of the conditions for repentance is for the one who committed Takhbeeb to seek absolution from the husband of the woman he corrupted, unless he fears a great harm, in which case he suffices with supplication and seeking forgiveness.