These distributions reach a plateau at $\Delta S \sim400-500$ pc in the galaxies (Fig. \[figure:classic2\]).

The obtained slopes are in close agreement with those previously found by @grasha2017. We can compare $ \Delta t - \Delta S$ relation for cluster pairs in NGC 628 as this galaxy is common for both our sample and the sample studied by @grasha2017. The result of @grasha2017: $\log \Delta t \sim (0.33\pm0.07)\log \Delta S$ for $\Delta S<600-950$ pc is consistent within errors with our fitting (see the thick dashed line, black circles, error bars, and the solid thin line in the top panel of Fig. \[figure:classic2\]). This is an additional argument in support of our cluster age estimates via $U-B$ colour.

The range of spatial scales for the galaxies in Fig. \[figure:classic2\] is larger compared to Fig. \[figure:age\_sep\]. This is due to the fact that graphs in Fig. \[figure:classic2\] show separations between all star clusters located randomly in the disc, whereas graphs in Fig. \[figure:age\_sep\] show separations of star clusters from H[ii]{} regions nearest to them. As a result, the spatial scale of cluster pairs in Fig. \[figure:classic2\] corresponds to the spatial scale of a galactic disc, whereas the spatial scale of SC-H[ii]{}R pairs 