Sorry to know about your brother. It's good that he is under treatment but the pontine glioma is mostly located to area called Pons which relay the message from brain to cerebellum which is for balancing and coordinations. Though he had taken chemotherapy still it needs time to heal.
Next Steps
For the time you can ask him to start with yoga as per his condition. do not force.
Health Tips
Go for specific follow-up physiotherapy. Thanks.