In various parts of the world there are societies in which a sister's son teases and otherwise behaves disrespectfully toward his mother's brother. In these instances the joking relationship seems generally to be asymmetrical. For example the nephew may take his uncle's property but not vice versa; or, as amongst the Nama Hottentots, the nephew may take a fine beast from his uncle's herd and the uncle in return takes a wretched beast from that of the nephew...
The nephew is disrespectful and the uncle accepts the disrespect. There is inequality and the nephew is the superior. This is recognized by the natives themselves. Thus in Tonga it is said that the sister's son is a "chief" (eiki) to his mother's brother, and Junod quotes a Thonga native as saying "The uterine nephew is a chief! He takes any liberty he likes with his maternal uncle!" Thus the joking relationship with the uncle does not merely annul the usual relationship between the two generations...the nephew's superiority to his mother's brother takes the opposite form of permitted disrespect.
"On Joking Relationships" (1940) A.R. Radcliffe-Brown
+Joking between Hui and Han Villages in China