Is the marriage contract valid, and what is its ruling if the husband discovers his wife's falsification of her birth date, meaning she is four years older than him instead of two? And would he be considered unjust to her if he marries another woman while they have seven children? And is he entitled to revoke the terms of the marriage contract related to the deferred dowry due to this falsification if a divorce occurs?

The marriage contract is valid and is not affected by the falsification of the wife's age. A slight difference in age does not establish the option of فسخ (annulment/dissolution). It is advised not to pay attention to this matter and to live with the wife with kindness (معروف). If the husband wishes to marry another, there is no impediment, provided he is capable of being just (عدل). Divorce should not be resorted to except after reconciliation becomes impossible. The falsification of age does not affect the wife's rights after divorce. It is advised to be patient, overlook minor faults, and focus on the good qualities of the wife for the continuation of affection, based on the Almighty's saying: "And live with them in kindness. For if you dislike them - perhaps you dislike a thing and Allah makes therein much good." (Quran 4:19), and the Prophet's (peace be upon him) saying: "A believing man should not hate a believing woman; if he dislikes one of her characteristics, he will be pleased with another."