Another way for these models to be distinguished might appear, if they were generically being included in some extended GUT. In contrast to many others, such a possibility appears for the chiral S U ( 3 ) F family symmetry (considered in the previous section) which could be incorporated into the family-unified S U ( 8 ) symmetry. Even if this S U ( 8 ) GUT would not provide the comparatively low S U ( 3 ) F family symmetry scale, the existence of several S U ( 5 ) × × S U ( 3 ) F multiplets of extra heavy fermions in the original SU(8) matter sector could help with a model verification. Some of them through a natural see-saw mechanism could provide the physical neutrino masses which, in contrast to conventional picture, may appear to follow both the direct or inverted family hierarchy. Others mix with ordinary quark-lepton families in a way that there may arise a marked violation of unitarity in the CKM matrix.