Brats are the children of the noble houses that reside above the wall and rule Hive Primus. Unlike the first and most important offspring however, they will never be expected to prove themselves as Spyrers in the cruel underhive, and will never take positions of real importance in the ruling of Necromunda. Some become bitter and hateful of their older siblings, some just accept the lack of responsibility and luxury, but some have a different approach. Although the noble houses try to stop this happening, groups of friends sometimes make a joint decision to sneak through the wall, usually bribing the guards, and living a life of daring adventure in the underhive. The Hivers call them Brats, but only behind their backs, because they see the whole of the underhive as a huge funhouse and will think nothing of blowing anyone away who annoys them with the sophisticated weaponry that they bring with them. Also above the wall there are no such things as Slaught, Nutz or Wildsnake, so they revel in the pleasures of the trading posts which they can afford in abundance. This makes them impulsive and maniacal at the best of times so you don't want to annoy a brat if you can possibly help it.
Although the noble houses are outside clan structure of Necromunda, they are not immune to the influence of the pervading treble culture of the hive world. Like the House Gangs, Noble houses have their own ancient and bitter rivalries which sometimes explode into violence. The root causes are often more to do with honour, traditional enmity, and dynastic disputes than the mainly economic and territorial causes of gang warfare in the lower levels of the hive.
The Brats are always in the forefront of any new fashion or cult that sweeps through the upper levels of the hive. Young nobles are privileged, wealthy, inquisitive, rebellious and open to wider influences than are available in lower levels of the hive. Brat gangs sport fantastic, elaborate costumes and hairstyles, and flout the conventions of the hive life as openly as possible.
In the upper level hive layers Brats run together in packs, but they do limit their predations to their home territories. They frequently drop down the spires into the lower habs, where their wealth can be used to obtain any drug or weapon. Once in the lower habs, the Brat gangs terrorize the techs and workers, safe in the knowledge that they can return to the upper habs whenever they what to.
Social Group - Brats are recruited from the unruly discontented and rebellious youth of the nobility.
Territory - The estates of the noble hoses in the Upper Hab layers.
Ritual - Brats go in for bizarre tribal rituals imitating those of the other hive gangs. Initiation rites, scars, tattoos, hairstyles and extravagant rather then practical clothing characterize these gangs.
Armament - Brats can be quite well armed due to wealth and access to imports. Exotic weaponry is especially favoured.
Motives - Brat gangs are mainly concerned with upholding the honour of their households. They also assume responsibility for "protecting' their territory from territory from uncouth lower hive dwellers. Brat gangs like to create a reputation for themselves by raiding other gangs. They also get up to various rebellious, subversive and anarchic activities including involvement with Cultists and Psykers.
From The Citadel Journal
These gangs are made up from Juves from the House gangs who have been cast out from their houses for their unruly and disruptive behaviour. They group together forgetting traditional rivalries and animosity of their Houses to cause as much trouble as they can and so they can survive.