Accident causer insurance does not pay… cause would not have paid his contribution…

Hello, I need your help 🙂 My brother had an accident, he was driven into the car by a child by bicycle. The situation on the right is clear, he is not guilty. The child is well. The accident was directed to the opposing insurance. This sent an expert, he set the amount of damage, with which my brother also agreed. Because he was told that the money would be transferred to his account and did not do anything about it, he called the insurance company. . And now the hammer, they told him that he does not get the damage compensated, because the mother of the boy did not pay the contributions…. That can not be?! He is not responsible for the collection of the open contributions, but the insurance?! And as long as the insurance of the woman does not cancel, after all also compensation claims must be paid, or do I see this wrong? Above all, they send first their own expert….and then something like that? Am to your Meinun? and thank me in advance. Anke