is too little to use statistical methods for galaxies NGC 3184 and NGC 5585. Therefore we analyse dependence $\log \Delta t - \log \Delta S$ for cluster pairs only in three galaxies: NGC 628, NGC 3726, and NGC 6946.

Fig. \[figure:classic\] shows the age distribution of star clusters in NGC 628 and NGC 6946. As seen from the histograms, star clusters are distributed by Gauss law with a little surplus of old clusters ($t>1$ Gyr). We excluded star clusters older than 300 Myr (they are marked by red colour in Fig. \[figure:classic\]) from the study of the $\log \Delta t - \log \Delta S$ dependence of cluster pairs, following @grasha2017. We do not show here the histogram for star clusters in NGC 3726, because of absence of clusters older than 300 Myr in the galaxy (see Fig. \[figure:age\_sep\]).

Obtained dependences for cluster pairs in NGC 628 and NGC 6946 resemble dependences between age difference and separation of cluster pairs found earlier in @efremov1998 and @grasha2017. We observe a growth of $\Delta t$ with increase in $\Delta S$ with slopes $0.52\pm0.12$ in NGC 628, $0.57\pm0.47$ in NGC 3726, and $0.30\pm0.11$ in NGC 6946 till the separations $\approx400-500$ pc in the galaxies. 