Distribution of the COSMOS X-ray groups in the halo mass versus redshift plane (open black circles). The filled magenta circles show the 95 groups with N ≥ 5 spectroscopic members which are used in this study. To inspect the redshift and halo mass evolution of the dynamics of BGGs and their satellites, we divide the hosting groups’ sample (magenta circles) into four sub-samples, marked with four dashed blue boxes and labelled S-I, S-II, S-III, and S-IV.