Preliminary comparison between the two first-ranked galaxies in CGs selected at z = 0. Left plots: Fraction of the two first-ranked galaxies in CGs whose rankings in absolute magnitude and stellar mass match. The bar plots are shown as a function of the SAMs and the assembly channels of their CG hosts. Right plots: Cumulative distributions of look-back times since the two first-ranked galaxies selected by stellar mass at z = 0 achieved their current ranking (only CG members at z = 0 are used). Each distribution is shown as a function of the assembly channel of the host CG. Vertical solid lines represent the median time for the two first-ranked galaxies to be considered under mutual gravitational interaction. Dashed lines indicate the median first pericenter time of the last-arriving CG member (key galaxy).