I have thin sunken in facial cheeks?

Most likely it's because your body m index is 17.6 putting you in an underweight category. Cheeks have a nice fat pad that causes the rounded shape, if you are able to gain more weight then you might find your cheeks round at as well. For some people they simply have incredibly fast metabolisms and a lean build where it is difficult to gain weight. But yes, take a look at your parents and you can get a good idea of how your body will age and where your metabolism goes from here. Be well.