What is the ruling regarding a man remaining married to a woman and her maternal aunt after they converted from the Shiite to the Sunni madhhab? Are their children legitimate or not? Is it permissible to marry his daughters from the second wife? And must a separation occur between the two wives?

It is impermissible to combine a woman with her paternal aunt or maternal aunt, by the consensus of Muslims. Immediate separation must occur between the husband and the wife who was married to her aunt, as her marriage is invalid. Ibn Taymiyyah said: "The marriage of the second [woman] is invalid; it does not require a divorce, nor does it necessitate a dowry or inheritance. If he has consummated the marriage with her, he must separate from her."

As for the children resulting from this invalid marriage, they are legitimate, their lineage is attributed to the father, and they inherit, because the husband believed the marriage to be valid, and "the child belongs to the bed."

Finally, it is permissible to marry the daughters of the second wife (from whom the husband has been separated), for they are legally his daughters.