The Collaborative International Dictionary of English v.0.48:
Jnr \Jnr.\ n. Abbreviation for Junior, used after a name by a son who has the same first and last name as his father; -- less commonly used than Jr. Syn: Junior, Jr. [WordNet 1.5]WordNet (r) 3.0 (2006):
Jnr n 1: a son who has the same first name as his father [syn: Junior, Jr, Jnr]