What is the ruling on a man marrying a woman while he is already married to her maternal aunt? Is this marriage considered void, especially since he has had children with her and cannot leave her or her aunt?

This marriage is forbidden by consensus (ijma') and is considered zina (fornication). If there is a doubt that would avert the corporal punishment (hadd) (such as not knowing of the prohibition), then the waiting period (iddah) is obligatory and paternity is established. However, if there is no such doubt (such as knowing of the prohibition), then, according to the majority of scholars, the child is not attributed to him, and the corporal punishment becomes applicable. Abu Hanifa holds that there is no corporal punishment on him, and paternity is established because the contract itself constitutes a doubt. According to the Malikis, paternity is established, and the corporal punishment is averted in the marriage of a woman with her paternal or maternal aunt, due to the difference in their prohibition by Sunnah compared to the prohibition of combining two sisters, which is forbidden by the Quran. It is obligatory for both of you to separate immediately and repent. You should resort to the Sharia court to rule on the issue of paternity.