What is the ruling on a woman going out with a married man, to whom she has become attached and who promises to marry her after divorcing his wife, but his family refuses?

You must repent, seek forgiveness, and feel remorse for illicit relationships with foreign men, and immediately cut off the relationship with the second man without hesitation, because the relationship between you is forbidden, and you should not be the cause of his wife's divorce. A sane man cannot marry a woman who has had previous illicit relationships from which she has not repented. If she repents, then there is no harm in marrying her after he obeys his mother and does not divorce his first wife. However, if she does not repent, she might engage in relationships with others. You must cut off the relationship with him without hesitation, seek Allah Almighty's forgiveness, and turn to Him to purify your heart. Allah may grant you someone better than him if your repentance is sincere. Do not follow your emotions, as they are harmful to your faith and worldly life, and your heart is ailing. Seek Allah's help, do many good deeds, and look for good company.