Warning: Spoilers ahead for both tonight's episode of The Flash and future episodes. Do not read on if you don't want to know.

During a screening of this week's episode of The Flash, titled "The Fury of Firestorm," last week, showrunner Andrew Kreisberg met with reporters to discuss the big revelations from tonight's episode -- including the nature of Wally West's connection to Iris.

Is that enough spoiler room?

Okay, so as we learned tonight, Iris's mother was pregnant when she left. She has a son. And as you've probably guessed, that's Wally West.

And, yes, it's Joe's son. So Wally is a heretofore-unknown full-blood brother of Iris West.

"We sort of had this idea, just like with any of the shows that we do, we kind of have these ideas in the previous season. We always knew we were leading up to this," Kreisberg said. "We always hated on TV shows where it's year two and somebody's, 'Well, Cousin John's coming,' and it's like, 'Oh, good old Cousin John,' who no one ever mentioned before. It was weird, the notion that they don't know Wally, and that was sort of where it came from. That was the idea that Francine was still alive and then that whole storyline."

And Iris, of course, spent much of last season pretty upset about the secrets that Joe and Barry were keeping from her...but now, she's responsible for keeping Francine's secret, and she doesn't like that, either.

"Iris is now in the position that Barry was in last season year," Kreisberg said. "She is keeping a secret to protect somebody. She's going to find that for all of her anger at Barry and Joe from last year, keeping this secret is not going to be so easy. It's going to be weighing on her before she finally decides to take some action in an upcoming episode."

More on that, one assumes, coming up soon...!