What is the solution to convince my brother to withdraw his divorce from his wife after three months of marriage, given his refusal to continue and the father's unsuccessful attempts to reconcile them?

It is advisable to sit with your brother calmly and speak frankly with him to understand the reason for his decision, promising him that you will understand his position and help him, and seeking the help of one of his trusted friends if necessary. If divorce is the solution, there is no objection to it. Your brother should be advised to obey his father and keep his wife, for perhaps Allah will bring much good through it, in accordance with His saying, the Almighty: "But if you dislike them - perhaps you dislike a thing and Allah makes therein much good." [An-Nisa: 19].