Praise be to Allah, the Lord of the Worlds, and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
My dear brother as you know ZINA (adultery and fornication) is among the biggest sins. Allah Says (Interpretation of meaning): " And come not near to the unlawful sexual intercourse, verily it is a FAHISHA (a great sin) and an evil way”. Allah has forbidden all things that may lead to this crime. He forbade looking at alien women, to enjoy her voice, to be alone with her, and other actions which may lead to HARAM. If you committed this big sin, you should repent to Allah and multiply your good deeds and supererogatory acts. Allah Says (Interpretation of meaning): {Except those who repent and believe (in Islamic Monotheism), and do righteous deeds, for those, Allah will change their sins into good deeds, and Allah is Oft- Forgiving, Most Merciful}. Since you have committed adultery with this woman, you should not marry her daughter. Allah knows best.