Is the mutual consent of both parties and a sound intention before God sufficient in the case of a man marrying a Woman of the Book, who has not been married for 15 years, while he is already married and his wife only fulfills her marital duties from time to time?

A woman does not become a man's wife except by fulfilling the conditions of a valid شرعي marriage, such as the guardian's permission, the presence of witnesses, and the marriage contract formula. A woman does not become a wife merely by offering herself to a man and the mutual consent of both parties. The questioner must separate from the woman and end the relationship with her, and repent if he has committed immorality. As for a wife's refusal to engage in intimacy without a valid شرعي reason, it is impermissible, and she is considered rebellious (nashiz). The questioner may marry another woman if he is capable of being just and fulfilling her rights.