What is the ruling of Islamic law regarding a man marrying a woman, then marrying her sister's daughter (the paternal aunt of the first wife's children), and having children from both of them, and what is the ruling concerning the inheritance of the children?

It is not permissible to combine a woman with her paternal aunt or her maternal aunt [in marriage], and this is by the consensus of scholars. If the marriage contract is concluded with both of them simultaneously, their marriage is annulled. If the marriage contract is concluded with one after the other, then only the marriage of the second is annulled. So, if a man marries a woman and her maternal aunt, the marriage of the second is invalid. However, if the husband was unaware of the prohibition, there is no sin upon him, and his children from this marriage are attributed to him.