Norms have been used to represent desirable behaviours that software agents should exhibit in sophisticated multi-agent solutions. An important open research issue refers to group norms, i.e. norms that govern groups of agents. Depending on the interpretation, group norms may be intended to affect the group as a whole, each member of a group, or some members of the group. Moreover, upholding group norms may require coordination among the members of the group. We have identified three sets of agents affected by group norms, namely, i) the addressees of the norm, ii) those that will act on it, and iii) those that are responsible to ensure norm compliance. We present a formalism to represent these, connecting it to a minimalist agent organisation model. We use our formalism to develop a reasoning mechanism which enables agents to identify their position with respect to a group norm, so as to further support agent autonomy and coordination when deciding on possible courses of action.