  Recent experiments by Guti\'errez $\textit{et al.}$ [Nature Phys.
$\textbf{12}$, 950 (2016)] on a graphene-copper superlattice have revealed an
unusual Kekul\'e bond texture in the honeycomb lattice --- a Y-shaped
modulation of weak and strong bonds with a wave vector connecting two Dirac
points. We show that this so-called "Kek-Y" texture produces two species of
massless Dirac fermions, with valley isospin locked parallel or antiparallel to
the direction of motion. In a magnetic field $B$ the valley degeneracy of the
$B$-dependent Landau levels is removed by the valley-momentum locking --- but a
$B$-independent and valley-degenerate zero-mode remains.
