It could be anything from a simple $200 fine all the way to time in jail. What he should expect is for the judge to make a decision and explain it to him. That’s why he’s going to court, in fact. If it was a standard fixed penalty, he would already know.
What he shouldn’t expect is any sympathy from the prosecutor or judge. Driving while suspended isn’t one of those things anyone can do by not paying attention, like speeding or forgetting to signal, it’s something that can only be done on purpose. Judges take a harsher stance on people who deliberately break the law.
Tell your brother to stop panicking and grow up. He knew the risk he was taking when he decided to drive, he gambled, and he lost.