Question about my tally wacker?

k ill rephrase my last question, Im 16 and i am 3.5 inches soft(non erect) and about 5 inches fully erect and i have heard of guys who are also 3.5 inches soft(non erect) who have 6 inch s or above. I'm wondering how come they can achieve that amount of growth and i can't even though we have the same soft length? Also i can feel another 2-3 inches of shaft in my pelvis when fully erect so will my grow another 2 or 3 inches?