Question is well he run into legal issues if the brother does not own the airplane?
Pretty much all light plane aircraft rental is done under Part 91. The FAA has absolutely no special rules about renting out airplanes. It's all insurance-driven. It only becomes a regulatory issue if you're providing flight training along with the plane, and then the only additional rule which comes into play is the requirement for 100-hour inspections....although can the owner "rent" the plane to his brother being part 91?
Sure, borrowing the plane is no problem insurance issues aside but pretty sure that he would not be able to "charge" for the use of the aircraft legally.
I was worried about the 100 hr rule. But that clarifies for me. First time in this situation.Pretty much all light plane aircraft rental is done under Part 91. The FAA has absolutely no special rules about renting out airplanes. It's all insurance-driven. It only becomes a regulatory issue if you're providing flight training along with the plane, and then the only additional rule which comes into play is the requirement for 100-hour inspections.