Is a man considered unjust towards his first fiancée by marrying another during the engagement period, and is he entitled to divorce her after an engagement that lasted three years and a marriage contract for one year, knowing that he had consummated the marriage with her before the wedding, and will he bear any sin towards her, and what should he do to please Allah given his choice between his second wife and his first fiancée, who swore she would supplicate against him after his marriage?

Your wife's family has no right to demand that you divorce your second wife, and you should not divorce her as long as the situation between you is sound. This marriage of yours is not an injustice to the first wife. If there was no condition against marrying another, then they have no right to demand a divorce. Even if there was such a condition, your wife has consented to your marriage. If the first wife requests a divorce for this reason, you are not obligated to grant her request unless she foregoes her dowry or a portion of it. If you wish to divorce her due to incompatibility, there is no blame upon you, as Ibn Qudamah holds that divorce is permissible when there is a need, such as due to a woman's bad character. We advise you not to divorce her, and to explain to her family that they have no right to demand her divorce, and that she must obey you. If she returns to you, you are obligated to be just between the two wives, and beware of inclining towards one over the other, for the Prophet, peace and blessings be upon him, said: "Whoever has two wives and inclines to one of them, will come on the Day of Resurrection with his side leaning."