You can also be genetically predetermined for a scant beard, even if your
testosterone is normal. This is largely due to genetic variations, ethnicity, and heredity. Keep in mind that you inherit genes from both parents. Your dad's beard may indicate what yours will be like, but so may your maternal grandfather's. Some men see their full beard come in when theyâre as young as 18 or 19. Others may continue to have sparse areas of growth until their mid-to-late 20s or even later. Shaving your beard is helpful for making it appear uniform and neat. Shaving does not, however, make beard hair grow faster. It also does not thicken it. The rate at which your beard will grow in, as well as its fullness, is largely determined by genetics, Testosterone and DHT also play important roles. Consult a Dermatologist for the same.