  We study two anisotropically interacting spins coupled to optical phonons; we
restrict our analysis to the regime of strong coupling to the environment, to
the antiadiabatic region, and to the subspace with zero value for $S^z_T$ (the
z-component of the total spin). In the case where each spin is coupled to a
different phonon bath, we assume that the system and the environment are
initially uncorrelated (and form a simply separable state) in the polaronic
frame of reference. By analyzing the {polaron} dynamics through non-Markovian
quantum master equation, we find that the system manifests a small amount of
decoherence that decreases both with increasing non-adiabaticity and with
enhancing strength of coupling; whereas, under the Markovian approximation, the
polaronic system exhibits a decoherence free behavior. For the situation where
both spins are coupled to the same phonon bath, we also show that the system is
decoherence free in the subspace where $S^z_T$ is fixed. To suppress
decoherence through quantum control, we employ a train of pi pulses and
demonstrate that unitary evolution of the system can be retained. We propose
realization of a weakly decohering charge qubit from an electron in an
oxide-based (tunnel-coupled) double quantum dot system.
