Hair naturally changing colour from Brown to Auburn. I'm 31 years old.?

Well I don't have any answers but if it makes you feel any better the same thing happened to my father and me so it must be genetic. My father started out life as a red-head turned brown than slowly darkened to black. I started life having black hair and slowly turned blond which as of know I still am. So I hope I at least showed you your not alone in the hair wierdness :)