I'm 22, my brother is 17
We both joined a gym and started working out on similar workouts for 3 months. September we changed up the workouts and he started following my new workout.

The only supplements my brother takes is a mega men multi-vit and a protein/glutamine shake post workout
I wake up the following morning somewhat in pain every once and awhile but my brother has NEVER felt sore and hasnt gained any considerable muscle weight.

The "new" workout consists of:
Mon- bicep curls, shoulder press, chest/military press, triceps, lat pull downs, rows, abs
Tuesday- squats, calf raises, leg extensions, hamstrings
Wed- cardio and abs
Thurs- (same as monday, minus abs)
Fri- (same as tuesday)
Sat-Sun- rest or cardio
(all sets are 15x3, abs are 25x4)

he doesnt get sore and doesnt see any real results.. hes starting to get tired of the gym bc he feels that his body hasnt changed in the last 4 months while ive lost 9lbs of fat and gained 11lbs of muscle

any idea on how he can change his workout to get the best results?