The Son Belongs to the Second Husband and the Choice is for the Husband Who Was Lost

Question :

A man was absent from his wife for a long period of time, until she believed he was lost. So his wife married another and she bore him a son. Then after some years, the first husband returned. Does her marriage to the second man continue, or is it annulled? And is it the right of the first husband to demand his wife back? And if it is permissible, is it necessary to make a new contract?

Answer:

This question concerns the marriage of the wife of a man who is lost: If the husband was lost and a length of time passed during which he was searched for, then it was ruled that he was dead, and she completed the prescribed period, then she married another, then he returned, he has the choice whether the marriage should continue or whether his first wife should return to him. If he allowed the marriage to continue as it is, then the matter is clear and the contract is valid. But if he did not choose this, and he wanted his wife to return to him, then she must return to him. But he should not have sexual intercourse with her until she has completed her prescribed period from the second one, and there is no need for a contract regarding the first husband, because there is nothing to invalidate his first marriage, that would require a new contract.

As for her child from the second husband, he is a legitimate child and he is attributed to his father, because it occurred as a result of a marriage which was permitted.

Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 5 Page 437