Marriage by shighar is defective and invalid

This is a letter that reached us from the listener (Q. L. Q) from Iraq, in which he has several questions. He says in the first one: My brother married a woman from among our relatives, and this woman's brother married my sister, meaning: it is a marriage by shighar. I, the questioner, know that there is no shighar in Islam, so what is to be done with this marriage? Is it forbidden on the grounds that it is shighar, knowing that both my brother and his wife's brother have each become the fathers of five children? I also wish to inform you that my aforementioned brother's wife is the daughter of my mother's paternal aunt. Is this forbidden or not? Please inform us, may Allah reward you?
Answer: Shighar is forbidden in Islam. The Prophet (peace and blessings be upon him) said: and he (peace and blessings be upon him) prohibited shighar. He said: This is shighar. If Zayd marries 'Amr's sister on the condition that he marries him his sister or his daughter, this is shighar. It is defective and invalid. It is obligatory for them to repent to Allah and seek forgiveness. If each one desires his wife, they renew the marriage without the condition of the second woman. If each one desires his wife and she desires her husband, he renews the marriage from her guardian without the condition of the other woman. Each one marries his female ward to her husband with a new marriage without the condition of the second woman. There is no need for divorce or anything else; because the water is his water and the wife is his wife by virtue of the contract he thought was a valid contract. So they must repent to Allah , and they must renew the marriage if each one desires his wife and she desires him. As for if she does not desire him, he divorces her with one divorce; because there is a doubt in the marriage. He divorces her with one divorce to cut off her attachment to him and his attachment to her, and to get out of the disagreement of those who validated it despite the sin. Yes, they must repent to Allah and they must renew the marriage if each one desires his wife and she desires her husband, with a new mahr, a new contract, and two just witnesses who attend the marriage. Yes.
The presenter: May Allah reward you.