What is the ruling on marrying someone who committed adultery previously and repented with sincere repentance? Is it permissible to marry without the family's knowledge, given that the fiancée is aware of this? What are the conditions for a repentant adulterer's sincere repentance?

The door of repentance is open for the fornicator and others, for Allah forgives all sins and loves those who repent. The conditions for sincere repentance are: abandoning the sin, regretting what has passed, and resolving not to return to it. If the fornicator repents, there is no objection for a woman to marry him, and the marriage is considered valid whether the fiancée and her family knew of his fornication or not.