Dark circles under the eyes can be hereditary; passed from one generation of a family to the next. This may be because your family has a tendency towards thin skin, to the development of extra pigmentation, fluids or fatty tissue, or that your family is prone to allergies. It could also be because you have inherited certain facial features. Or it could simply be that your family all have dark circles under their eyes for no discernable reason.
Whatever the hereditary cause of dark circles under the eyes, there is very little that can be done to prevent or cure it. There are a number of tips and techniques given throughout this site that you can use to reduce or conceal them.