Simple: Tell your brother to act smart and not as if it's his first time to fly out of the country. If the culprits sensed a single scent of fear, i'm telling you, they'll take their opportunity and take the bite...especially now that they know that most of the people going to Qatar on business/personal visa intends not to come back and instead work there. Keep the communication open, and be ready to call and talk to the immigration officer if needed. Just ask them straight what is the reason why he should be hold for departure, worst comes to worst. unless he's a criminal or produced a falsified document, can they hold him from leaving the country.

It's not because things are difficult that we don't dare, it's because we don't dare that makes things difficult!