The paper confronts Georg Simmel’s distinction between the dyad and the triad with the phenomenological analysis of analogous structures undertaken by E. Lévinas, B. Waldenfels, and J.-L. Marion. Simmel insists on keeping the dyad and the triad apart while only the triad is considered worthy of sociological research. On the contrary, phenomenologists reveal deep interrelation between the relationship with the other and the third party where the latter is actually co-present in the dyad. The presupposed link between the two and (...) the three implies a different understanding of sociality that would respect its members in their uniqueness, unlike the world of interchangeable individualities common for social science. The third party can appear as the dimension of law and the ordinary, as the other of the other and the figure of humanity, or as the child in the case of erotic relationship. The last aspect of the third party provides a link to family studies. A brief outline of the situation illustrates oscillation between the triadic and dyadic interpretations of the family with the apparent prevalence of the dyad in recent decades. (shrink)