There are plenty of women in the world, and Allah has not placed any hardship or restriction upon you in this matter. Seek a wife elsewhere without causing harm to your sister.
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Question: I have already married one of my relatives, and her father married my sister in exchange. Is such a marriage permissible, bearing in mind that each woman received a dowry of money and a she-camel? Please tell me: is this marriage valid in its present form, or is it a shighar marriage? May Allah reward you with the best.
Answer: If each woman received a dowry equal to the customary dowry for someone in her position, was not deprived of any part of her right, and the contract was concluded with her full consent and free choice—each woman willingly accepting the other man and experiencing no coercion—then the marriage is valid and faultless.
However, if this reciprocal marriage took place without the consent of the two women, or involved infringing a woman’s right by reducing her dowry or omitting it altogether, then it is a shighar marriage and is impermissible.
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Marriage to the Daughter of One’s Father’s Wife
Question: A man married a woman who bore him a son and then passed away. He later married another woman who had a daughter from a previous husband, and this second wife bore him two sons. The son whose mother had died then married the daughter who had become a sister to his two half-brothers. Is this permissible or not? Please advise us—may Allah grant you goodness.