  All the possible three-family ${\cal N}=1$ supersymmetric Pati-Salam models
constructed with intersecting D6-branes from Type IIA orientifolds on
$T^6/(\mathbb{Z}_2\times \mathbb{Z}_2)$ are recently presented in arXiv:
2112.09632. Taking models with largest wrapping number $5$ and approximate
gauge coupling unification at GUT scale as examples, we show string scale gauge
coupling unification can be realized through two-loop renormalization group
equation running by introducing seven pairs of vector-like particles from
${\cal N}=2$ sector. The number of these introduced vector-like particles are
fully determined by the brane intersection numbers while there are two D6-brane
parallel to each other along one two-torus. We expect this will solve the gauge
coupling unification problem in the generic intersecting brane worlds by
introducing vector-like particles that naturally included in the ${\cal N}=2$
sector.
