  Based on a maximally symmetric minimal unification hypothesis and a quantum
charge-dimension correspondence principle, it is demonstrated that each family
of quarks and leptons belongs to the Majorana-Weyl spinor representation of
14-dimensions that relate to quantum spin-isospin-color charges. Families of
quarks and leptons attribute to a spinor structure of extra 6-dimensions that
relate to quantum family charges. Of particular, it is shown that 10-dimensions
relating to quantum spin-family charges form a motional 10-dimensional quantum
space-time with a generalized Lorentz symmetry SO(1,9), and 10-dimensions
relating to quantum isospin-color charges become a motionless 10-dimensional
quantum intrinsic space. Its corresponding 32-component fermions in the spinor
representation possess a maximal gauge symmetry SO(32). As a consequence, a
maximally symmetric minimal unification model SO(32) containing three families
in ten dimensional quantum space-time is naturally obtained by choosing a
suitable Majorana-Weyl spinor structure into which quarks and leptons are
directly embedded. Both resulting symmetry and dimensions coincide with the
ones of type I string and heterotic string SO(32) in string theory.
