Many Brood Brother units have the option to be lead by a Genestealer Hybrid, assigned by the Magus to oversee the faithful and inspire them to greater acts of bravery. This will be noted in the unit description, along with which types of Hybrids are allowed as a Leader for the unit and the extra points cost for that model. A unit can be lead by only a single Hybrid Leader, and the Leader can never leave the unit. Hybrid Leaders are armed with a Laspistol or Autopistol, wear Flak Armour (5+ Save), and can select items from the Armoury as normal. Note that a Hybrid Leader is not an upgrade of an existing model in the unit – it is an additional model.
Hybrid Leaders
Source: Codex: Genestealer Cult, p. 5