Well, this sounds familiar.
A couple of years ago, The Flash introduced Barry Allen and Iris West's daughter from the future, a character we came to know as Nora Allen/XS (played by Jessica Parker Kennedy). Unfortunately, the machinations of Reverse-Flash meant that she was ultimately wiped from existence and the timeline.
Now, though, Barry and Iris are getting another shot as being parents as they meet their future son: Bart Allen. Of course, this is a departure from the comic books as that version of the teenage speedster is their grandson (and the son of Meloni Thawne and Don Allen). Jordan Fisher (To All The Boys 2) will play the character, and he'll make his debut in The Flash's 150th episode.
That's the seventeenth episode of the show's current seventh season, for those of you wondering!
"The future son of Barry Allen and Iris West-Allen, Bart is the fastest teenager on the planet," reads the description. "Due to Bart’s penchant for wildly impulsive behavior, a stunned Barry and Iris will have their hands full trying to teach their new son patience. But it’s a task they’ll have to accomplish, in order for their family to work together and stop Team Flash’s biggest threat yet"
It's certainly an interesting, albeit familiar twist, and if Grant Gustin's time as the Flash is nearing its end (as many have speculated), Bart could very easily become the show's new lead. For now, all we know is that he'll have a key role to play in this landmark episode of The CW series.