'Fast 9' gives Dom a younger brother fans never knew about. Here's why we're just learning about Jakob Toretto for the first time in 20 years.

• Warning: There are major spoilers ahead for "Fast 9."
• John Cena joins the cast as Dom's little brother, Jakob Toretto, who we've somehow never heard about.
• Inspired by a personal moment in the director's life, a major event drove a wedge between the two.

"Fast 9" introduces fans to Dom and Mia's younger brother Jakob. Somehow, in 20 years of the "Fast & Furious" franchise, we're only meeting Jakob (John Cena) for the first time noq.

But there's a pretty good reason the youngest Toretto hasn't been around.

Since 2001's "The Fast and the Furious," we knew Dom's father, racecar driver Jack Toretto, famously died in the middle of a race in a fiery blaze.

Shortly afterward, Dom beat the man responsible for causing Jack's crash badly enough to end his racing career. As a result, Dom was banished from the racetrack and sent to prison for two years.

The start of "Fast 9" finally takes fans back to 1989 to show the moment Dom lost his father and the dark events that followed, which not only sent Dom to jail but into a life of crime.

Where Jakob has been: A major life event sent him into exile.

In "F9," we learn that Dom has always blamed Jakob for their father's death.

While in jail, Dom meets longtime "Fast" franchise members Leo and Santos while fixing up a car. They tell him to be careful because he can cause the car to explode if he makes one simple mistake. The thought gives Dom the idea that Jakob purposefully killed their dad the day of the race by making a change under the hood of his car.

(What Dom didn't realize back then was that his dad asked Jakob to help him throw the race, resulting in his accidental death.)

Blinded by rage, when a young Dom gets out of jail, he challenges Jakob to a car race. If Jakob wins, he can return home to live with Dom and Mia. If he loses, he's to never return. Dom easily wins and exiles Jakob from the Toretto family.

Though Mia says she stayed in touch with Jakob for a little while, she eventually lost touch and couldn't track him down.

Jakob, meanwhile, became the James Bond of the franchise. He started working for Mr. Nobody (Kurt Russell), the same guy who recruited Dom and the gang in 2015's "Furious 7." Jakob worked as a spy for years until he went rogue for undisclosed reasons we hope to learn in a future "Fast" sequel.

By the end of "F9," the bad guys turn on Jakob. He's now on the run from Cipher and others who are likely hunting him down since he tried to take over the world (not an exaggeration).

Dom, after being told the entire film that he can't let hate consume him when it comes to family, decides to give Jakob a second chance by giving him a Charger, a symbol of the Toretto name at this point, as an escape vehicle.

The two share some level of respect for one another as they part ways, but they're a long way from being best buds.

The story was inspired by the director's life.

When he returned for "F9," director Justin Lin said he knew they needed "an incident that is worthy of this sense of banishment" for Jakob to never have been mentioned in any other film.

When asked if there was any real-world influence that helped make this story a reality, Lin told Insider, "There was something definitely happening to me in my personal life that kind of inspired the exploration into this."

Without getting too specific, Lin told Insider that his relationship with his two siblings is "one of the most complicated and intense relationships to this day."

"There's certain things I can't let go," Lin said. "My siblings ... I don't want to say it's a mess, but it's a mess."

Lin said because the story element was personal, it was something that came together rather quickly for the film.

Will we see Jakob again? Cena's down to return.

Although there's no word on if Cena will reprise his role in a future "Fast" film, the actor who portrays Dom's long lost brother wants to see this storyline through.

"I would love to see more Jakob," Cena told Insider when we asked him if there's a chance he'll return.

"As the rookie on the squad, I'm not near high enough to make any of those decisions," he added. "I just really hope that the world enjoys 'F9.' If they enjoy it, maybe I'll get another shot."

It certainly seems like Dom and his crew could use someone with Jakob's spy skill set to take down Cipher and any other villains who may come after the family.

"Fast 9" is in theaters now. You can read our review here.