  Dynamics of symmetric and antisymmetric 2-solitons and 3-solitons is studied
in the model of the nonlinear dual-core coupler and its PT-symmetric version.
Regions of the convergence of the injected perturbed symmetric and
antisymmetric N-solitons into symmetric and asymmetric quasi-solitons are
found. In the PT-symmetric system, with the balanced gain and loss acting in
the two cores, borders of the stability against the blowup are identified.
Notably, in all the cases the stability regions are larger for antisymmetric
2-soliton inputs than for their symmetric counterparts, on the contrary to
previously known results for fundamental solitons (N=1). Dynamical regimes
(switching) are also studied for the 2-soliton injected into a single core of
the coupler. In particular, a region of splitting of the input into a pair of
symmetric solitons is found, which is explained as a manifestation of the
resonance between the vibrations of the 2-soliton and oscillations of energy
between the two cores in the coupler.
