My little brother is in high school and is upset that he dosent have a deep voice yet. he has already started growing hair. how long till the voice?

Hard to say: The process of puberty can start and finish in 3 years or 7. Along the way the common features come out when they will. It can be said that the longer the transition the more time the kid has to grow taller, because the full process also stops linear growth. You might tell him to be patient. Most would rather be taller & his wish to reach that point could have a negative impact on his stature.