The basic kinship unit of brother and sister constitutes a theme ranging from the mundane to the spectacular and from the licit to the illicit. In spite of the seemingly infrequent occurrence of Motif P253 as reported in the two standard indexes, the sister and brother theme appears with great frequency in folk traditions as well as in all other facets of culture and society. The explicit listings of the presence of the brother-sister theme in the various units designated in Aame and Thompson's The Types of the Folktale is incomplete. In tale types, the brother-sister theme is less overt; nonetheless, it plays a significant psychological role in the development of the narrative's plot. In narrating a tale, a tale-teller may be confused about who is who among its personae, unwittingly revealing brother-sister incest. Arabic literature is replete with expressions of affection and strong bonding between brother and sister.