Green’s Dictionary of Slang

(UK black) any younger person, spec. a junior gang member.

2013		K. Koke ‘Fire in the Booth’ 🎵 Thirty goons came to bridge and ran out / I had to tell my youngers stand down.
2017		theculturetrip.com ‘Guide to London Slang 10 Jan. 🌐 Younger – sibling, someone younger than you.
2020		G. Krauze What They Was 21: Man like Bunny [...] raise up the youngers and show them how to live .