  The spectrum and dominant strong decay properties of the doubly heavy baryons
are revisited by using a chiral effective model with chiral partner structure.
By regarding the doubly heavy baryons in the ground states and light angular
momentum $j_l = 1/2$ sector of the first orbitally excited states as chiral
partners to each other, we estimate the mass splitting of the chiral partners
which arises from the spontaneous breaking of chiral symmetry to be about $430$
MeV for baryons including an unflavored light quark and about $350$ MeV for
that including a strange quark. We point out that, similar to the heavy-light
meson sector, the intermultiplet decay from a baryon with negative parity to
its chiral partner and a pion is determined by the mass splitting throught the
generalized Goldberger-Treiman relation. Furthermore, the isospin violating
decay of $\Omega_{cc}$ baryon, $((1/2)^-, (3/2)^-)_s \to ((1/2)^+, (3/2)^+)_s +
\pi^0$ through the $\eta$-$\pi^0$ mixing is the dominant decay channel of the
doubly heavy baryons including a strange quark.
