  We present a supersymmetric (SUSY) model based on trinification
$[\mathrm{SU}(3)]^3$ and family $\mathrm{SU}(3)_\mathrm{F}$ symmetries embedded
into a maximal subgroup of $\mathrm{E}_8$, where the sectors of light Higgs
bosons and leptons are unified into a single chiral supermultiplet. The common
origin of gauge trinification and of the family symmetry from $\mathrm{E}_8$
separates the model from other trinification-based GUTs, as it protects, in
particular, the Standard Model fermions from gaining mass until the electroweak
symmetry is broken. Furthermore, it allows us to break the trinification
symmetry via vacuum expectation values in $\mathrm{SU}(3)$-adjoint scalars down
to a left-right symmetric theory. Simultaneously, it ensures the unification of
the gauge and Yukawa couplings as well as proton stability. Although the
low-energy regime (e.g. mass hierarchies in the scalar sector determined by a
soft SUSY-breaking mechanism) is yet to be established, these features are one
key to revive the once very popular trinification-based GUTs.
