Origin of family symmetries
  Discrete (family) symmetries might play an important role in models of elementary particle physics. We discuss the origin of such symmetries in the framework of consistent ultraviolet completions of the standard model in field and string theory. The symmetries can arise due to special geometrical properties of extra compact dimensions and the localization of fields in this geometrical landscape. We also comment on anomaly constraints for discrete symmetries. 
Hans Peter Nilles, Michael Ratz, Patrick K.S. Vaudrevange
hep-ph hep-th