What is the ruling on a man, who is illicitly cohabiting with a woman and has children with her, performing an Islamic marriage contract (Aqd Shar‘i)? And what are the conditions for that? And what is the ruling on someone who wishes to embrace Islam but has a Muslim mistress who has stipulated that he must convert to Islam first?

The fundamental principle is to assume Muslims are truthful. If a person requests a marriage contract and you are unaware of them having committed fornication, the inquirer is not obligated to investigate their past relationships. If the conditions for a valid marriage—a guardian and two just witnesses—are met, the contract is permissible.

However, if one is aware of fornication, scholars have differed regarding the necessity of a waiting period (istibra') before the contract, and there is latitude in this matter. Anyone who declares their Islam is subject to the rulings applicable to Muslims and may marry from among the Muslims.