  We propose that the dark matter of our Universe could be sterile neutrinos
which reside within the twin sector of a mirror twin Higgs model. In our
scenario, these particles are produced through a version of the Dodelson-Widrow
mechanism that takes place entirely within the twin sector, yielding a dark
matter candidate that is consistent with X-ray and gamma-ray line constraints.
Furthermore, this scenario can naturally avoid the cosmological problems that
are typically encountered in mirror twin Higgs models. In particular, if the
sterile neutrinos in the Standard Model sector decay out of equilibrium, they
can heat the Standard Model bath and reduce the contributions of the twin
particles to $N_\mathrm{eff}$. Such decays also reduce the effective
temperature of the dark matter, thereby relaxing constraints from large-scale
structure. The sterile neutrinos included in this model are compatible with the
seesaw mechanism for generating Standard Model neutrino masses.
