We investigate the twelve-dimensional gauge-Higgs unification models with an
eight-dimensional coset space. For each model, we apply the coset space
dimensional reduction procedure and examine the particle contents of the
resulting four-dimensional theory. Then, some twelve-dimensional SO(18) gauge
theories lead to models of the SO(10)\times U(1) grand unified theory in four
dimensions, where fermions of the Standard Model appear in multiple generations
along with scalars that may break the electroweak symmetry. The representations
of the obtained scalars and fermions are summarized.Comment: 17 pages, 4 table