Throughout the series, GTA protagonists often interact with each other; the results can either be friendly or deadly.
Until recently, GTA protagonists mainly kept to themselves. Older games took place in different time periods which meant interactions were rather unlikely. However, this doesn't mean there weren't any. It's slightly more common than one would think, and that's not even counting the player characters in GTA 5.
These are the GTA protagonists who met each other throughout the series. An honorable mention goes to Tommy Vercetti and Victor Vance, who briefly met during a drug deal. They only had a few seconds before the latter was gunned down, forcing Tommy to retreat.
Five different times GTA protagonists interacted with each other
5) Franklin, Michael, and Trevor (GTA 5)
For the first time in the series, players would control multiple GTA protagonists in a single game. Niko, Johnny, and Luis had their own games, but they weren't integral to their respective plots. Franklin, Michael, and Trevor were different as the entire story revolves around them.
Michael and Trevor already had a history with each other. Upon learning the other is alive, their strained relationship takes up the majority of the story. Meanwhile, Franklin has to work with them to resolve their differences. All of them meet each other by improbable luck.
They must work together in several missions, since they often share the same enemies. Ultimately, Franklin has to decide their fates. According to the GTA Online canon, all these GTA protagonists end up surviving.
4) Niko, Johnny, and Luis (GTA 4)
GTA 4 has three different stories between the main game and its DLC episodes. Niko Bellic worked together with Johnny Klebitz, mainly as enforcers in criminal dealings. A diamond trade goes wrong when Luis Lopez crashes the party, forcing them to flee. This is the one time they all meet in the same place.
Unbeknownst to Johnny, Niko ends up killing his best friend Jim Fitzgerald but he never finds out about it. On the flip side of the coin, Johnny also kidnapped Niko's cousin Roman. It should be noted that Johnny was forced to do so as Dimitri Rascalov was holding his girlfriend hostage.
Among these GTA protagonists, Luis barely interacts with Johnny. However, he does run into Niko when the latter robs the Bank of Liberty. Roman also entered his nightclub at one point.
3) Claude and Toni (GTA 3)
At this point in time, Toni wasn't one of the GTA protagonists. He was a boss character who gave missions to Claude. During GTA 3, Toni had Claude take care of business with the Triads as they were interfering with his operations.
Claude performs several missions for the mafia. However, he lacks any loyalty to them. Salvatore Leone tries to get him killed, but Claude survives the attempt. GTA 3 players need to finish the mission string for Toni beforehand. Otherwise, they will miss out on 100% completion.
After Claude severs his ties with the mafia, he personally kills Salvatore himself. While it's unknown what became of Toni, the rest of the mafia turned hostile to Claude. He can't even walk their streets without shotguns blasting him away.
2) CJ and Claude (GTA San Andreas)
CJ and Claude were never on good terms. They are among the few GTA protagonists to have been with the same lover. This distinction is shared with Niko and Luis (Carmen Ortiz), along with the GTA 5 protagonists (random booty calls).
Catalina ends up pulling them into conflict. When she breaks up with CJ, she ends up with Claude, but they proceed to challenge each other to a street race. CJ ends up winning, along with a property deed in San Fierro. It's unknown what Claude was doing there prior to meeting with Catalina.
Ultimately, Catalina loves no one but herself. She betrays both CJ and Claude in their respective games. Among the GTA protagonists, CJ and Claude are the only ones to date a main antagonist.
1) Trevor and Johnny (GTA 5)
Trevor is rare among GTA protagonists. He manages to kill another with his bare hands. For context, the Lost MC eventually moved from Liberty City to Blaine County, which was run by Trevor. He worked with Johnny Klebitz to sell drugs and weapons.
It was a one-sided relationship. Trevor would regularly sleep with Johnny's girlfriend Ashley. He also ordered GTA Online protagonists to steal Lost MC supplies. Trevor had no good intentions for Johnny, who was physically and mentally destroyed by drug abuse.
During a bad mood, Trevor puts the outlaw biker out of his misery. He ends up stomping his brains out on the desert road. Johnny and Victor are the only GTA protagonists to die a premature death.
Note: This article reflects the writer's personal views.