Were the front rubber brake lines replaced? If not that could be the problem. Some times with old brake lines the inside layers of the rubber will split, crack, colapse inside. This will allow the fluid to flow to the caliper/wheel cylinder but not allow the pressure to be released when you let off the brake pedal, keeping pressure on that one brake.
If it does it again slide under there and crack the bleeder valve. If fluid squirts out and brake pads/shoes release then that is the problem.
My sons 77 C10 has a brake line doing this now that I need to replace and it doesn't do it all the time, which would explain why your brother had no problem when he drove it.
Good luck.
