As far as the fictional Fast & Furious world goes, F9 revealed that Dominic and Mia had an estranger brother named Jakob, played by John Cena. I won’t share any specific spoilers for what goes down between the siblings, but with the way F9 ends, Dom and Mia could easily cross paths with Jakob again in Fast & Furious 10 and/or Fast & Furious 11. F9 also provided Jordana Brewster the opportunity to take part in more action-packed scenes, a welcome break from Mia having traditionally either been on the sidelines or serving as a damsel in distress. Dom may want to keep her safe, but she knows how to handle herself both in a fight and behind the wheel of a car.
