A father giving his sister in marriage to a man in return for marrying his son to the other's daughter

Q: It was destined by Allah for someone to propose to my father that his son should marry my father's sister. My father agreed to this on the condition that the man would let me marry his daughter. Both marriages were in fact concluded a long time ago without any specified Mahr (mandatory gift to a bride from her groom) being paid to either bride. A condition was written in the marriage contract stating that if the bride proves to be a good wife, she will stay with her husband, otherwise her family will pay an amount of money for her not being a good wife.Two years ago, there was some kind of misunderstanding between my aunt, whose marriage my father agreed to, and her husband. Her husband forced her to leave his house and she is now still living with her brother. A short while after this, my wife’s father and brothers incited her to leave my house and the two wives have now been in their families’ homes for about two years. My aunt’s husband and I married again about a year ago and we each have children with our new wives. Our first wives, are now deserted and they have no desire to return (Part No. 18; Page No. 430) to us and my aunt’s husband and I are comfortable with our new wives and have no interest in our first wives, because of the misunderstanding that took place between the families. The first wives are the victims of this misunderstanding.We that hope Your Eminence will give a Fatwa (juristic opinion from a qualified Muslim scholar) about the rulings on Al-Badal marriage (a reciprocal marriage when “A” marries “B's sister” provided that “B” marries “A's sister”) and the continuing desertion of the first wives in their families’ homes.

A: It was Haram (prohibited) for your father to give his sister in marriage to someone in return for you marrying the other man’s daughter without either wife receiving a Mahr. This kind of marriage is called Shighar marriage (exchange of daughters or sisters for marriage with no mandatory gift to a bride from her groom) and it is obligatory for the matter to be referred to a judge for the necessary steps to be taken to annul the marriages and for a ruling to be made on the amount that each wife has a right to for the consummation of the marriages. Once this has been done, the wives will no longer be deserted and will be free to marry anyone they consent to among the men who are lawful for them to marry. Regarding the condition laid down in the marriage contract - that the woman who proves to be a good wife should remain with her husband or her Waliy (a legally accountable person acting for a woman regarding marriage) should pay an amount of money for her not being a good wife - is a Batil (null and void) condition. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.