  This work considers the remarkable suggestion that the three families of
quarks and leptons may be unified, together with the Higgs and gauge fields of
the Standard Model (SM), into a single "particle", namely the $\textbf{248}$
vector superfield of a ten-dimensional $E_8$ super Yang Mills (SYM) theory.
Towards a realistic model along these lines, a class of orbifoldings based on
$T^6/(\mathbb{Z}_N\times \mathbb{Z}_M)$ are proposed and explored, that can in
principle break $E_8$ SYM down to the minimal supersymmetric standard model
(MSSM), embedded in a larger group such as $E_6$, $SO(10)$ or $SU(5)$, together
with other gauge group factors which can be broken by Wilson lines. A realistic
model based on $T^6/(\mathbb{Z}_6\times \mathbb{Z}_2)$ is presented. The
orbifold breaks $E_8$ SYM down to a Pati-Salam gauge group in 4d, together with
other gauge groups, which are further broken to the SM by Wilson lines in the
right-handed sneutrino directions, yielding proto-realistic fermion mass
matrices, and experimental signals associated with a low Pati-Salam gauge group
breaking scale.
