  We present the multiple stellar systems observed within the SpHere INfrared
survey for Exoplanet (SHINE). SHINE searched for substellar companions to young
stars using high contrast imaging. Although stars with known stellar companions
within SPHERE field of view (<5.5 arcsec) were removed from the original target
list, we detected additional stellar companions to 78 of the 463 SHINE targets
observed so far. 27% of the systems have three or more components. Given the
heterogeneity of the sample in terms of observing conditions and strategy,
tailored routines were used for data reduction and analysis, some of which were
specifically designed for these data sets. We then combined SPHERE data with
literature and archival ones, TESS light curves and Gaia parallaxes and proper
motions, to characterise these systems as completely as possible. Combining all
data, we were able to constrain the orbits of 25 systems. We carefully assessed
the completeness of our sample for the separation range 50-500 mas (period
range a few years - a few tens of years), taking into account the initial
selection biases and recovering part of the systems excluded from the original
list due to their multiplicity. This allowed us to compare the binary frequency
for our sample with previous studies and highlight some interesting trends in
the mass ratio and period distribution. We also found that, for the few objects
for which such estimate was possible, the values of the masses derived from
dynamical arguments were in good agreement with the model predictions. Stellar
and orbital spins appear fairly well aligned for the 12 stars having enough
data, which favour a disk fragmentation origin. Our results highlight the
importance of combining different techniques when tackling complex problems
such as the formation of binaries and show how large samples can be useful for
more than one purpose.
