Paul Walker’s untimely death has meant that Brian and Mia are no longer a part of the story, and characters like Han, Gisele and others have been killed off, but the whole core premise in the Fast and Furious movies is family, and Dom, Letty and Roman, as well as characters like Tej and Hobbs these days, have maintained a core unit in the movies.
One way that Fast and Furious stands out from a lot of other long-term projects is that the franchise has maintained a relatively stable cast over the years.
Not every popular franchise–on TV and in the movies–gets the luxury of churning out movies on a fairly regular basis, much less keeping the majority of its leads while it does that.