Motorcycle accident, not my bike, bike insured, who is liable? Long read, please help....?

Insurance follows the vehicle so if the bike was indeed insured (collision) then the insurer should pay for the damages on the bike less the stated deductible amount and the damage to the car. Your brother needs to do the right thing and pay the deductible amount to his friend. This is all uming he is at fault. A ticket for improper turn is probably a indicator that he will not get off the hook for this one.