The hair growth is genetic. However, the way you treat it in the first years affects the way it is later in life.
I don't quite get what you mean by your face being covered. Do you shave? If your facial hair has started to grow, you should shave. It is not good to wait for it to mature - it will take ages and the beard may remain thin.
Regular shaving will stimulate the hair, but don't expect bushy mustache or beard too soon.
Mine has matured around 25 years old. By that time I didn't want to have any of it on my face
Also, if you shave with the razor, try to do it properly - along the hair. Avoid the temptation to shave sideways even if it makes the skin extra smooth. The hair gets accustomed to the shave direction and sideways shaving turns from the option to necessity. I did this mistake, now I use the electric shaver because I just can't shave my neck sideways without cutting myself in several places.