Fraction of particles that share progenitor galaxies between the ICL (blue) and BCG (orange). A high shared fraction means that a large number of particles in the ICL originate in progenitor galaxies that also contribute to the BCG and vice versa. The top panel shows the overall shared fraction, while the bottom two panels divide the shared fraction of progenitors from completed mergers (middle) and progenitors from surviving galaxies (bottom).