In syntax, c-command relations make explicit reference to binding phenomena. A node is said to c-command its sisters and all the daughters of the sisters. (Carnie, 2006, p. 127) Nodes may be c-commanded symmetrically or asymmetrically.
When two nodes c-command one another, this is an instance of symmetric c-command. In contrast, a node that c-commands her nieces and their descendants is an instance of asymmetric c-commanding. (Carnie, 2006, p. 127-129)
Carnie, A. (2006). Syntax: A generative introduction. John Wiley & Sons.
Lai, I. S. (1998). The grammar and acquisition of Secwepemctsín independent pronouns. [Master’s thesis, The University of British Columbia].