What is the ruling of the Sharia on an uncle who committed adultery with his mahram? Is it permissible for him to prevent her marriage to a person who has repented from drugs and is addicted to smoking? And is she obliged to agree to this marriage, knowing that she loves her uncle?

You have committed a major crime and a great evil by engaging in immorality with your niece. You must hasten to repent and feel remorse, and avoid meeting her, being alone with her, touching her, or looking at her. You should know that you are afflicted with the disease of passionate love, and you must hasten to marry, repent from smoking and abandoning prayer, and increase in good deeds.

Similarly, the girl must repent to Allah for what she did with you, regret it, and never return to anything like it. She must honor her father, obey him, and try to please him, repent from disobedience, and not leave her home except with his permission.

If the man who proposed to her has repented from his transgression and his repentance is sincere, she may accept him. As for you, do not interfere in her engagement, as her matter rests with her father.