There is strong evidence that the occurrence of mutually very nearby stars with identical spectral type and apparent magnitude is in many cases appreciably more frequent than one has reason to expect if there should only be a case of pure random combination. This phenomenon might be associated with the problem of stability of small stellar systems, if we can identify a certain number of the coincidences as some sort of cluster remnants. Besides the fact that there are several physical explanations of the coincidence phenomenon without consideration to dynamical stability conditions, there is also more than one stability aspect which may be regarded as reasonable. In the first instance we have to survey the possibilities that the stability of certain conglomerations of stars - particularly those with two components - may depend on the mass relation and will reach a maximum value for equal masses. As most straightforward we regard the conception that the most massive stars in a cluster (or even a multiple system) form the most stable and hence the most long-lived configuration, so that a cluster remnant most probably will consist of stars of rather equal mass.