If my underbite is hereditary (i got it from my grandfather), it can't be fixed with braces alone, can it? if my jaw is the problem?

Skeletal Issues: If the jaw size discrepancy is skeletal in nature, then you need to correct it surgically, not orthodontically. If the discrepancy is minor, then orthodontics may help correct the bite somewhat. Your best bet is to consult with an orthodontist/oral surgeon team since each case is different and no one answer applies to everyone.

Need evaluation: A Class III Malocclusion, with a jaw-size discrepancy, usually requires both braces and jaw surgery to correct. Ask your General Dentist t refer you to a qualified Orthodontic Specialist to answer your questions. The Orthodontist will have an Oral Surgeon to recommend to you for additional input. See both to get all your questions answered.

Yes it can: We actually fix lots of underbites without requiring surgery & with only braces. A lot depends on how severe the underbite is. No one will be able to tell until you see an orthodontist. Some orthodontists also shy away from these cases as they are difficult, so if the first one you see says you need surgery, I would at least get a second opinion (maybe even a 3rd if it means avoiding surgery)

You may need surgery: Frequently underbites are hereditary, and often they do need surgery for correction. Sometimes, if the underbite is slight (only 1 to 3 millimeters) it can be corrected with braces alone.

Depends: Depends on many factors. Get opinions from more than one board certified orthodontist. Be careful. Some orthodontists try to "save" you from surgery. And you end up getting a compromised cosmetic result. Also get an opinion or two from board certified oral & maxillofacial surgeons.

Maybe it can....: A mild underbite, with a functional shift, can frequently be treated very well without surgical intervention. Sever underbite will usually require surgical aid to correct properly. I treat many classIII malocclusions, underbite, without surgery with very nice results. Seek out a couple of opinions to see what your options are.