Magnetoelastic effects measured previously on Ce x La 1- x B 6 were reanalyzed based on the dynamical Jahn-Teller effect as a single site effect and the paired distortion as an interaction effect developed in recent papers for RB 6 in general. In the dilute systems, we observe an anomalous Curie-Weiss term caused from competition between the single site effect and the pair effect, while in the dense systems anomalies due to pair formation are observed even in the paramagnetic region. Strong frustration inherent to the pair ordering plays an important role. Anomalous properties in PrB 6 and NdB 6 were also interpreted based on the above common model in good agreement with the experimental results, in particular with anomalous neutron scattering measurement. Magnetoelastic effects were measured also on PrB 6 and NdB 6 . In PrB 6 the effect is 100 time stronger than that in CeB 6 due to induced mixing through distortions between the nearly degenerated ground levels, Γ 1 and Γ 5 . The charge dipolar ordering ...