- "They are dead! All of then! Inbred hillbilly twats."
- — Trevor about the O'Neil Brothers
The O'Neil Brothers are a family of inbred, hillbilly, redneck meth dealers in Grapeseed, Blaine County. They are familiar with the Varrios Los Aztecas gang, with The Lost MC and with Trevor Philips, a drug and arms dealer also based in Blaine County with his own company, Trevor Philips Enterprises, whom the O'Neil Brothers are rivals with.
Events of GTA Online
The O'Neil brothers appear in the heist setup mission Series A - Steal Meth, where the GTA Online Protagonists steal a tanker full of meth juice from them that is used by Chef to create the meth lab in the Liquor Ace gas station for Trevor Philips Enterprises. They later appear in the Series A Funding finale, attacking Trevor and the GTA Online Protagonists along with the other gangs that were ripped off by them.
Events of GTA V
After some potential clients, the Los Santos Triads, decide to work with the brothers instead of Trevor due to his violent and reckless behavior. This angers Trevor so much that he attacks O'Neil ranch and singlehandedly kills most of the family, save Elwood, Walton and Wynn, who left before the attack, and destroys their ranch by blowing up the meth lab in the basement. Following this, Trevor starts receiving phone calls from one of the brothers, threatening him with death.
Some time after, Franklin calls Trevor and informs him that he is following the rest of the vengeful O'Neil brothers along the Great Ocean Highway near North Chumash. Trevor informs Franklin that he and Michael are coming to Franklin's position.
The O'Neil brothers soon drive into Raton Canyon, with Franklin still in pursuit. A doe steps into the O'Neil's path and they swerve to miss it, causing their car to crash. Franklin, with Chop in tow, exits his Baller and goes to the crash site, only to discover that the O'Neils have disappeared into the woods.
Michael uses a sniper rifle with a thermal scope to kill Walton and Wynn O'Neil but then Elwood starts firing rockets at the helicopter. Franklin then uses Chop to find and kill Elwood. Alternatively, once Franklin chases Elwood and his cover is blown, the player can shift to Michael and snipe Elwood from the helicopter, killing him.
- GTA V
- Trevor incorrectly lists Don (instead of Dan) as one of the O'Neil Brothers in "Predator". He also mentions a possible additional brother named Dalton though Elwood did not mention him in Crystal Maze. He may have meant Walton, however, but since there were more than 10 guards at the meth lab it's possible that 2 of the un-named O'Neils were Don and Dalton.
- When killing a O'Neil Brother in Crystal Maze, sometimes another one will say something like "Ned?! Ned?!", possibly another member of the O'Neil Brothers. In addition another O'Neil Brother will say that "Cletus is down" and "Chester is down." Larry is another possible brother as the name can be heard during the shootout.
- During the Series A Heist, Trevor sends the Protagonist to the O'Neil farm to steal their kush. During the Heist setup, the Protagonist kills most if not all the brothers, however they appear alive and well in the main game several months later. It's possible Rockstar just reused the O'Neil character models, or killing the O'Neils in Online is non-canon.