Hi
You are right in that facial structure/ bone, chubby cheeks ,hypertrophied jaw muscle, a weak Chin as well as Aging changes due to gravitational descent and volumetric changes in the facial fat Compartments can lead to a wider or broader lower face .
Depending on the assessment the following are possible
1. Neurotoxin like Botox or Xeomin to the masseter to reduce the bulk causing the face to slim down.
2. Chin augmentation with fillers to created a more pointed look and when combined with the above can create a V shaped effect in the lower face.
3. HIFU devices like Ultraformer III to shape and contour the jowls and lower face.
4. Fillers to contour and shape the lower face.
5 Threadlifts to create a V shape effect.
Hope this helps