By Samantha Simon
Updated Sep 21, 2016 @ 9:00 am
Ron Batzdorff/NBC/NBCU Photo Bank

Warning: Major plot spoilers from the series premiere of This Is Us below.

If you tuned in to the series premiere of This Is Us last night, then no doubt your head is still spinning from the emotional whirlwind of an episode. Seriously, just one hour in and we’re already so emotionally invested in these characters that we may as well have been watching them for years. In the NBC series, Justin Hartley plays Kevin, a TV actor who stars (mostly sans shirt) on a laugh-track sitcom and seemingly lives the good life—but Kevin is much deeper than he initially appears.

“He’s a very interesting character, even though he doesn’t necessarily look it at first glance,” Hartley recently told InStyle. “He’s got the money, the job, and the power. He lives in L.A and seems like he’s doing fine, but when you scratch the surface, you see he’s coming to that age where he’s starting to understand how other people perceive him—and it’s not at all how he imagines himself being perceived.”

For starters, “Kevin considers himself a serious actor, an artist, and a really nice guy who treats his sister well,” said Hartley. “But he’s looking at his life, and these people are laughing at him and wanting him to take his shirt off. He doesn’t really have a significant relationship with a woman anymore than he did ten years ago, and he’s looking at his life now at 36 and wondering what the big difference is from when he was 26. And it’s really just this goofy show that he’s on. So he’s at this crossroads where he’s starting to question everything and figure out what his next step is and what he wants out of life.”

Paul Drinkwater/NBC/NBCU Photo Bank

At the end of the first episode, we got a bit more insight into Kevin, as well as the rest of the show’s characters, with the revelation of a major plot twist that will shape the entire series moving forward. We learned that while Kevin is living in the present along with his sister Kate (Chrissy Metz) and Randall (Sterling K. Brown)—who is ultimately revealed to be their adopted brother—the storylines of Rebecca and Jack (Mandy Moore and Milo Ventimiglia) are actually set in the past.

As for the newborn babies we watched the couple welcome? Well, they grew up to be the trio of characters we’ve been following all episode—and that shocking discovery even caught the stars off-guard when they first saw the script. “I had no idea when I read the entire episode,” said Hartley. “Then at the very end, I was like, Aha! I literally had to go back about four pages, because then I thought I might have been confusing the characters, but then I realized what was happening. It’s much easier to ‘get’ when you’re watching it, because [the show’s creator] Dan Fogelman writes it for the screen—not to be read on paper.”

After realizing the dynamic between the characters (including the depressing fact that when Randall mentioned his late adoptive father, he’s talking about Jack), we asked Hartley what it’s like to have Moore and Ventimiglia portray his mom and dad. “Milo and Mandy are my parents—that’s kind of cool,” he said. “It’s so funny, because I’m not really working with them much. I see them a lot on set, but I’m not in the scenes with them, obviously. So we haven’t gotten around to joking about it, but it’s only a matter of time before I start calling Milo ‘Dad.’” The irony there? “Milo and I are pretty much the same age—he’s actually a couple of months younger than me, and then Mandy’s much younger,” said Hartley. “So it’s interesting. But they’re good parents, right?”

VIDEO: Everything to Know About This Is Us, Straight from the Show’s Stars

So far, we vote yes—but sadly, the decades of difference between the characters means that we’ll likely never get to see them share the screen. “I don’t know what they’re going to do in the future,” said Hartley. “I’m not in that circle of decision-making, but I guess they’ll have to age the actors or cast older actors to play them. If they decide to age them, then there’s a chance that I would get to work with Milo and Mandy—but as of now, we’re on totally different work schedules for our scenes. It’s odd, because it’s cool to be on a show with them, but it’s depressing not to be able to work with them!”

While Moore and Ventimiglia may be in a totally different world onscreen, their characters’ actions will directly affect who their children ultimately became. And we’ll get to see exactly how these characters are shaped. “You’ll find out stories about the parents and how that influences each of the kids,” said Hartley. “And we’ll definitely dive further into the relationships these characters have with their parents and with each other. You’ll see how they remember things going when they were children, and why they have certain rifts.”

One rift affects Kevin in particular. “Sterling’s character and my character don’t necessarily see eye to eye on a lot of things, and they have different versions of what happened when they were kids,” said Hartley. “So you have this really cool story of how these two kids that are the exact same age, grew up with the exact same parents in the exact same neighborhood, and lived in the exact same house, have completely different lives and completely different perspectives on things. They ended up not really getting along that well, and it’s sort of interesting to see that—and now my character has this longing to reconnect, so we’ll see how that goes.”

The relationship between Kevin and his sister will be explored as well. “You have these two twins who sort of rely on each other maybe a little too much, and they have this codependency thing going on,” said Hartley. “There’s a moment where they decide to see what they can each do on their own for the very first time, and when it comes to Chrissy’s character’s story, you see her work through her weight and body issues and try to find love with this guy who’s really cool and struggling with the same things, but has a totally chill take on life. You get to watch how she deals with that—does she self-sabotage, does she figure it out, does she move forward, or is she scared? They’re all just going to stumble and fall and pick themselves up, and you’re going to laugh along the way in between your crying as you dive deeper into these characters and try to figure out what the hell they’re all about.”

And despite the fact that the pilot packed some huge revelations, there are still plenty of curveballs heading our way. “In every episode, we have a ‘What?’ moment,” said Hartley. “Some are big and some are small, but there’s one in every single episode. Some are surprises, some are revelations. They’re not all, “Oh my god, what is this big twist?”—but there’s a moment at the end of every show that you won't see coming.”

Catch This Is Us Tuesday nights at 10 p.m. ET on NBC.