An explicit SU(12) family and flavor unification model with natural   fermion masses and mixings
  We present an SU(12) unification model with three light chiral families, avoiding any external flavor symmetries. The hierarchy of quark and lepton masses and mixings is explained by higher dimensional Yukawa interactions involving Higgs bosons that contain SU(5) singlet fields with VEVs about 50 times smaller than the SU(12) unification scale. The presented model has been analyzed in detail and found to be in very good agreement with the observed quark and lepton masses and mixings. 
Carl H. Albright, Robert P. Feger, Thomas W. Kephart
hep-ph