Does a man's touching of his fiancée with lust, which led him to believe she became forbidden to him due to ideas related to "رضاع الكبير" (adult breastfeeding), prevent their marriage despite their desire to repent?

First: It is not permissible for the suitor to touch the fiancée, be alone with her, or kiss her, because he is a stranger to her until the marriage contract is concluded. What was mentioned about touching the breasts and similar acts is forbidden and repentance for it is obligatory.

Second: These matters do not render the girl forbidden (for marriage), even if he suckled from her, because suckling by an adult has no effect. What is meant by sucking the breast is the suckling of milk, not merely kissing without milk coming down.

Third: The best cure for obsessive thoughts (waswasah) is to constantly engage in remembrance of Allah (dhikr), to be diligent in prayer, and to remain steadfast in obedience, and then to turn away from the obsessive thoughts.