The list of possible double and multiple open clusters between galactic
  longitudes 240 and 270 degrees
  This work studies the candidate double and multiple open clusters (OCs) in
the galactic sector from l = 240o to l = 270o, which contains the Vela-Puppis
star formation region. To do that, we have searched the most recent and
complete catalogues of OCs by hand to get an extensive list of 22 groups of OCs
involving 80 candidate members. Gaia EDR3 has been used to review some of the
candidate OCs and look for new OCs near the candidate groups. Gaia data also
permitted filtering out most of the field sources that are not member stars of
the OCs. The plotting of combined colour-magnitude diagrams of candidate pairs
has allowed, in several cases, endorsing or discarding their link. The most
likely systems are formed by OCs less than 0.1 Gyr old, with only one eccentric
OC in this respect. No probable system of older OCs has been found. Preliminary
estimations of the fraction of known OCs that form part of groups (9.4 to 15%)
support the hypothesis that the Galaxy and the Large Magellanic Cloud are
similar in this respect. The results indicate that OCs are born in groups like
stars are born in OCs.
