Is it permissible for a wife whose husband went missing in Syria to marry his brother, especially since the period of his disappearance has reached three years and two months and problems continue to escalate between her and her in-laws, or is she required to wait until the period reaches four years?

The basic principle is that a woman is under the authority of her husband. Therefore, it is not permissible for her to marry her husband's brother or anyone else unless she is certain that the husband's authority has ceased. The rulings concerning the wife of a missing person involve a lengthy disagreement among jurists. Hence, it is advisable to consult the Sharia court so that the judge can take the necessary measures and rule appropriately, because a judge's ruling resolves disagreements in matters of ijtihad (independent reasoning), and it is not sufficient to rely solely on a fatwa in this matter.