Life insurance paid out benefits incorrectly

Benefits were to be paid out to two grandchildren who are brothers. Three months ago the insurance company paid the full benefit to a single brother. The company admits its mistake. However it is telling the 2nd brother that it is up to him to collect from the first brother.

Is it truly the brother's problem to settle? Or should the insurance company be responsible for paying the 2nd brother his correct benefit and then claw back their mistake from the 1st brother?