  The Einstein-Podolsky-Rosen (EPR) steering, which is regarded as a category
of quantum nonlocal correlations, owns the asymmetric property in contrast with
the entanglement and the Bell nonlocality. For the multipartite EPR steering,
monogamy, which limits the two observers to steer the third one simultaneously,
emerges as an essential property. However, more configurations of shareability
relations in the reduced subsystem which are beyond the monogamy could be
observed by increasing the numbers of measurement setting, in which the
experimental verification is still absent. Here, in an optical experiment, we
provide a proof-of-principle demonstration of shareability of the EPR steering
without constraint of monogamy in the three-qubit system, in which Alice could
be steered by Bob and Charlie simultaneously. Moreover, based on the reduced
bipartite EPR steering detection, we verify the genuine three-qubit
entanglement. This work provides a basis for an improved understanding of the
multipartite EPR steering and has potential applications in many quantum
information protocols, such as multipartite entanglement detection and quantum
cryptography.
