my little brother is 15 and i was wondering if he may be able to come to the gym with me this summer. he is extremely big for his age, complete opposite of me. about 6 ft tall and very heavy though not extremely obese but defnitely needs some help. i was wondering if i might be able to take him 3 or 4 days per week for some weight training. is 15 too young? i dont want to hurt him in the long run