How can I broaden my forehead? I want to fill my temples for a wider forehead.

Thank you for your question. I suggest that you move forward and consult with a board certified facial plastic surgeon.
Best wishes,

If you are seeking to fill in temples for wider forehead, the most natural way would be by fat graft. Your own fat can be harvested from your thigh or abdominal area, and injected on the forehead and temple area. 
Fat grafting technique and know how is the most important part in order for the fat cells to remain longer.