maybe they've been training longer?? How strong is your bench press? If not that great work on gaining strength! If you for example can bench press 100 for 5-8reps, your chest will be significantly bigger if your work your way up to benching 150+ for 5-8reps.
If you already have a very strong bench, well then theres other factors we need to look more closely at like training program/diet/body stats ect ect.