What can I do for a stronger jawline? My cheeks have always been full and chubby, causing jawline to be almost invisible (photo)

For a more defined jawline to strengthen your profile (and help prevent the dreaded jawline "jowl" sagging), we use injectable fillers like Revanesse Versa - a filler known to limit swelling and give subtle, soft enhancements - or Radiesse. Using a cannula to limit pain and swelling, we inject on the bone in strategic points to get more lift and shaping, resulting in a more contoured lower face and defined, structured jawline. I would suggest getting a formal evaluation with a facial sculpting expert. Best, Dr. Emer

Hello,  Thank you for your question and photo. Based on what can be seen here,  it appears he would benefit from a filler like Voluma or Sculptra.  These products are strong enough to enhance the structure of the face. They could be used to create a stronger jawline.  As always, please consult with a local, experienced physician to determine the best course of treatment. Good luck! 

 Hi, I have performed many facial shaping procedures using dermal fillers, silastic facial implants (cheek, chin and or lip implants), liposuction and/or facelifts for over 30 years.  From the photos, your cheeks are very flat in the front, the chin is weak as are the back portions of the jaw line.  
 Following my beauty principles, women look the most feminine, youthful and attractive with heart shaped faces.  Heart shaped faces have cheeks that are full and round in the front.  Cheek augmentation with a dermal filler or using cheek implants for a permanent enhancement will create full, round cheeks that will feminize the entire face.
 I have performed many Chin Augmentations using chin implants for over 30 years.  From the photos, your chin is weak.  A weak chin creates an imbalance making the nose appear larger, the mid face top heavy and the lower face look short that de-emphasizes the lips and allows early formation of a double chin.  Chin augmentation using a chin implant will add projection to the chin creating harmony and balance to the lower face. 
 I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty.  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  In my opinion, you are a good candidate for chin implant surgery.
 The back portion of your jaw line is a bit weak and can be augmented, without making your face appear masculine, using precise placement of a dermal filler (I prefer using Restylane Lyft).  
Hope this helps.