  Elastic neutron scattering, ac susceptibility, and specific heat experiments
on the pyrochlores Er$_{2}$Ge$_{2}$O$_{7}$ and Yb$_{2}$Ge$_{2}$O$_{7}$ show
that both systems are antiferromagnetically ordered in the $\Gamma_5$ manifold.
The ground state is a $\psi_{3}$ phase for the Er sample and a $\psi_{2}$ or
$\psi_{3}$ phase for the Yb sample, which suggests "Order by Disorder"(ObD)
physics. Furthermore, we unify the various magnetic ground states of all known
R$_{2}$B$_{2}$O$_{7}$ (R = Er, Yb, B = Sn, Ti, Ge) compounds through the
enlarged XY type exchange interaction $J_{\pm}$ under chemical pressure. The
mechanism for this evolution is discussed in terms of the phase diagram
proposed in the theoretical study [Wong et al., Phys. Rev. B 88, 144402,
(2013)].
