Br.

Noun

 * 1) An abbreviation of Brother, a title used before either a given name or surname for an adult male, especially in a religious or fraternal context.
 * Br. John Doe

Usage notes
This is the customary abbreviation of this term as used in case citations. See, e.g., [https://www.law.cornell.edu/citation/4-900.htm § 4-900. Documents from Earlier Stages of a Case] from Introduction to Basic Legal Citation (online ed. 2015)