The sense of 'we' is a feeling of comfortableness, of belonging. Differences between groups are maximized, differences within are minimized, ignored or denied. Membership places constraints on behavior of both dominant and subordinate groups. Both are defined by their relationship to each other. Symbols are important to maintain group solidarity and definition.
Groups differ to the degree that they recognize all three ways of being a member.
Membership is sometimes defined as being a member of a family in the society and sometimes defined by being considered a member of the state whether one is a member of a family or not. In some societies there many be differences in access to benefits depending on whether one was born into the group or joined the group as an adult. The boundaries between members and non-members is important and permission to cross those boundaries must be given and recognized.