The shared madness or Folie à deux was described in France in the nineteenth century by Charles Lasage and Pierre Falret, as a condition where a person (the primary) builds a delusional system, sharing it with another (the secondary), who must be very close to the first affected, becoming delirious with the same subject. Several theories attempt to explain the phenomenon that challenges theories of personality structures, rooted in relational and/or environmental features of psychosis. Theoretically, there are many attempts to classify this psychotic experience: in some manuals they distinguish various types of partners: the simultaneous psychosis, where the two people start to became delirious at once; imposed psychosis, in which the disorder arises first with one, then going on to “healthy” individual and symptomatology disappears after being separated; and communicated psychosis, where the first transmitted the psychotic experience to the second, and he or she develops his or her own delusion not interrupted even while separated. Other classifications about shared madness not only between two people, but three, and four, even a whole family show us how complicated the delirium systems can become. In our paper, we will discuss the different theories explaining this rare psychiatric condition based on a case about two brothers of 35 and 37, who live together with the rest of the family, and also come together to the same mental health center, although with different psychiatrists.