  The purpose of the present work is a detailed investigation of the dynamical
evolutionof Collinder 135 and UBC 7 star clusters. We present a set of
dynamical numerical simulationsusing realistic star clusterN-body modeling
technique with the forward integration of thestar-by-star cluster models to the
present day, based on best-available 3D coordinates and velocitiesobtained from
the latest Gaia EDR3 data release. We have established that Collinder 135 and
UBC 7 are probably a binary star cluster and have common origin. We carried out
a full star-by-star N-body simulation of the stellar population of both
clusters using the new algorithm of Single Stellar Evolution and performed a
comparison of the results obtained in the observational data (like cumulative
number counts), which showed a fairly good agreement.
