'Los Hermanos' (Spanish for 'The Brothers'), is one of "many" gangs operating in and around the city of Tijuana, Baja California, Mexico. They are featured in the Season 2b comic con trailer -- as does the name it is assumed applies to them.
It is unknown whether or not 'Los Hermanos' existed before the outbreak or if they formed from the remains of other gangs to fill the void left by the civil authorities.
'Los Hermanos' seem to control large territory in and around the city of Tijuana. They apparently have an arrangement with the members of La Colonia. The La Colonia provide medication and medical help, while Los Hermanos provide food. It is unknown to what degree they hold the same beliefs as Celia Flores and La Colonia, or if they hold them at all.
Members of the gang (or at least, members of their families) are drug addicts. When members of Los Hermanos attack Nicholas Clark for 'stealing' a candy bar, Nick was able to talk his way out of punishment by reminding them he supplied 'Oxy' to the addicts (Los Muertos).
The gang has been described as "the worst of men," who are excited about the infected because they represent "the lawless world they have been waiting for."