Sorry to hear that.
Ask your brother to keep reciting
1. Hasbunallahu wa naymal wakeel.
2. La ilaha illa anta Subhanaka, inni kuntu minaz-Zwalimeen
Insha`Allah he will be out soon.
Before one of the many actions the Pak governments have taken against Lashkare Tayyaba (without foundation, and eventually government cases having been thrown out, as there was no evidence of wrongdoing), I chanced upon a lashkare tayyaba office in Karachi. As I was anticipating another government action against them, I asked the young men there what would they do if the government shuts down their organisation and puts them in jail. They weren't concerned, and said they would continue their dawah in the jail.
So whatever the circumstances, Allah (swt) will provide him an opportunity to earn merits for the final life ahead all of us.