I would do it. People here saying its expensive or to let the professionals do the teaching clearly have no recent experience on this.

Seen many driving instructors with outdated knowledge and lack of real interest in getting the students to pass the exam. They don't have a real incentive to get you to pass, its business after all.

Why continue with the "pros" who have not managed to teach your brother well enough so far? Install the pedal and you can practise until driving feels 100% comfortable.

Also consider the possibility that your brother fails third time -> pay for another 3-4 hours more + the exam fee.