The Fast & Furious franchise has always been about family, so it was only fitting that family be important in the first spinoff movie Hobbs and Shaw. The movie introduced a sister for Jason Statham's Deckard Shaw and gave Dwayne Johnson's Luke Hobbs a lot of brand new backstory, including a large extended family in Samoa. We even got to meet his mom.
His mom was played by actress Lori Pelenise Tuisano, but it seems that, if Dwayne Johnson had wanted to make real family a big part of Hobbs & Shaw he could have done so, as he revealed in the Blu-ray special features of the film that his real life mother wanted to play his mom in the movie as well. According to Johnson...
My mom would ask me every other day, ‘Well, how come I can’t play your mom?’ Well, ‘cause you’re my mom, actually, in real life, and you’re not really an actress. She’s like ‘No, but I act all the time.’
It is true that Ata Johnson has her own IMDb page, but it's basically full of credits of Dwayne Johnson's mom playing herself as she has occasionally appeared on various WWE programs in association with her son. She's not a professional actress and obviously, that's what Hobbs & Shaw needed, but if the movie had wanted to cast an unknown in the role, mom was apparently more than willing.
Of course, really, if Ata Johnson wanted to be in Hobbs & Shaw she has nobody else she needs to convince except her son. Johnson was also a producer on the film, so he certainly could have cast her in the role of his mother if he'd wanted to. Clearly, it's all his fault that we didn't get the real mother and son interaction.
And if you're curious why Dwayne Johnson's mother was asking him every other day about being in the movie, it's because, based on footage from the Blu-ray special features, Johnson's mother was actually on the set of Hobbs & Shaw during the scenes that are set in Samoa, which were actually filmed in Hawaii. All the more reason he should have cast her, if she was going to be there anyway, you might as well put her to work.
The closest we get to Hobbs & Shaw starring actual family of Dwayne Johnson, is the role of brother Mateo, played by Joe Anoa'i. Anoa'i goes by Roman Reigns in WWE and while he and Johnson are not technically related they refer to each other as cousins due to a close bond between the two families that have worked in professional wresting for generations. The Blu-ray also reveals that the character of Mateo actually had lines in the movie at one time, though they are all cut from the final edit.
Hobbs & Shaw is now available on Digital HD and will be released on Blu-ray November 5