Spatial distribution of the 20 PMS stars (circles) in the sky area towards the CO Cepheus void, overplotted on the visible extinction A_V, RQ map of Planck Collaboration XXIX (2016)⁷. We display the Cep III members as blue circles and those still gravitationally bound (i.e., Cep II that is a subgroup of Cep III, see Sect. 4.2) as cyan circles, while the non-members are shown in red. The big hexagon encloses the Cep I members. The asterisks mark the locus of the three additional members reported in Oh et al. (2017) and Faherty et al. (2018), as described in Sect. 4.4.