Why do some people have fuller lower faces and some people have very "chiseled" lower faces? Is it limited to genetics?

You are right, genetics is a big factor in this- genetics can mean that you have a recessed chin, or a poorly defined jawline, that can further exacerbate lower face fullness. Weight gain can also make the lower face appear fuller from excess fat in the area of the neck and cheeks. Buccal fat reduction is a good way to reduce or contour the lower face, as well as other procedures that can define the jawline and neck (fillers, implants) or procedures such as liposuction  to remove fat along the jawline and neck and different options for skin tightening of the lower face (noninvasive such as ultherapy to invasive such as facelifts). Restoring volume to the upper face can improve the lower face contour by elevating skin- so that has to be the primary cause of your full lower face- for that to work. Treatments will be determined based on what exactly is going on with your particular face, and can be determined at a consolation with your doctor. 

Thank you for sharing your excellent question.  Genetics plays the largest role in your facial appearance as a result of its effects on your bone and soft tissue structure.  Though adjustments can be made with minimally invasive and surgical options they still are limited by your starting position.  You may be able to reduce this area with a combination of buccal fat removal and cheek fillers but much can also be accomplished by camouflaging the area with chin and jawline filler, Kybella, and Botox.  See an ASPS board certified plastic surgeon in consultation to discuss. h

May factors:- genetics- lifestyle- diet- sun exposure- smoking- medication effectsToo many to list.  You can control everything except the genetics.

The shape of a face is genetically determined, as well as the way they age. Aesthetic medicine as well as surgery can help to modify certain features such as increasing cheek volume with fillers, or decrease fat in buccal area or chin to modify the jaw line. You need to consult with an experienced physician in order to address your concerns. Also facial features are different in women and men and it is very important to keep this in mind when trying to modify your appearance.