Unfortunately, there is a lot of individual variability in the development of the male sexual organs, even between members of the same family.
If, at the age of 16, you have already developed pubic hair, and hair in your armpits, then you probably have normal testicular function (if you have not developed these "secondary sex characteristics," then you may need to see an Endocrinologist to be tested for hypogonadism (decreased sex hormone secretion by the testicles)).
Also, at the age of 16, your body is still actively developing, and, therefore, the current state of your genital development may still "progress" over the next few years.
If you can find a male pediatrician who specializes in the care of teenagers, this might be a good place to begin.
Sincerely/ Robert A. Wascher, MD, FACS
http://doctorwascher.com