  We report the measurements of spin alignment ($\rho_{00}$) for $K^{*0}$,
$\overline{K^{*0}}$, $K^{*+}$, and $K^{*-}$ vector mesons in RHIC isobar
collisions (Zr+Zr and Ru+Ru) at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV. We observe
the first non-zero spin alignment for $K^{*\pm}$ in heavy-ion collisions. The
$K^{*\pm}$ $\rho_{00}$ is about 3.9$\sigma$ larger than that of $K^{*0}$. The
observed difference and the ordering between $K^{*\pm}$ and $K^{*0}$ are
surprising, and require further inputs from theory. When comparing between the
isobar and Au+Au collisions, no significant system size dependence in $K^{*0}$
$\rho_{00}$ is observed within uncertainties.
