If you allowed him to do buy the ring with your account, then it was his legal gift (his gift of something he lawfully purchased with your permission) to her, and a gift, once given, cannot be ungiven. She gets to keep the ring unless some other arrangement is come to in the divorce (e.g. they agree that he'll get the ring back in a divorce agreement). If there was an agreement between you and your brother that he'd reimburse you for the ring, you can enforce that agreement (even if an oral, or unwritten one) in court if necessary.If your brother did NOT have permission to use your account, he committed theft. IF you are willing to file a police report and press charges against him, you may be able to get the ring back and/or deny the charge (though much depends on how long it's been; if you did not act quickly when first discovering the theft, then it could easily be held that it was *not* a theft, but rather a permitted use, and one where you are simply after the fact changing your mind about it). But again, you'd have to report your brother for theft; if you won't, no one will believe it was a theft.