EXCLUSIVE: 'This Is Us' Star Justin Hartley Talks Kevin's Rocky Reunion With Ex-Wife, Warns of a 'Dark Turn'

There have been plenty of surprises on This Is Us. But none more so than Kevin’s shocking revelation that he was once married to his childhood sweetheart.

Tonight’s brand new episode, titled “I Call Marriage,” explores the theme of marriage in its all its beauty and ugliness, from Kevin’s desire to reunite with his ex-wife and Kate’s young engagement to Toby, to Jack and Rebecca’s big day and possible marital strife between Miguel and Shelly. For Kevin, attempting to start anew with Sophie (played by Alexandra Breckenridge) marks a new beginning for the former Man-ny star.

“The more you get to know him, he’s not at all what I thought he was at first glance,” Justin Hartley tells ET ahead of Tuesday’s episode. “This whole thing Kevin’s fighting is this perspective that other people have of him and him being like, ‘That’s not me.’ And yet, here we are as audience members looking at him and going, ‘He’s totally different than what I thought he was.’”

RELATED: 'This Is Us' Composer Reveals His Secret to Making You Cry

“As a viewer, you’re experiencing the same thing that Kevin is experiencing in his real life and you’re watching it all happen. It’s hard not putting people in boxes, right?” the 40-year-old wonders. “I like that he has an ex-wife and that he has textures and that he’s lived. He’s not just a guy who hasn’t had a lot of life experiences.”

So what can fans expect from Tuesday’s episode? Hartley took some time out of his Monday morning to dish on how his perspective on Kevin has changed since the ex-wife reveal, his theories on what pushed them apart and why there are more storm clouds ahead for the Pearson brood.

ET: We have so much to unpack! The last episode featured a surprise with your character, Kevin, who we find out was once married to his one true love, Sophie. How did finding that out change your perspective on Kevin?

Justin Hartley: It did, definitely. At first glance, he’s just this guy who had these meaningless relationships -- if you even want to call them relationships -- and he probably doesn’t have a lot of friends and he probably doesn’t have prospective girlfriends, nothing really going [in his life]. Then you start to dig a little bit deeper, and you realize he’s a very deep guy. The ex-wife thing is really cool -- his one true love who he’s been in love with since he was 10 years old. At first, you think that’s not that guy. But once you get to know him a little better, you’re like, of course that’s Kevin. He’s a huge love bug. This guy is all heart and I love that about him. To tell the story about why they broke up, what happened with their marriage, why aren’t they married anymore and what went wrong there, that’s going to be a cool story to tell.

Early in the season, it seemed Kevin had a relatively easy life and was going through the motions. Was his speech in on Sophie’s doorstep the first truly raw moment where saw the real Kevin?

It started when he was describing the painting to his nieces. That was the first time you may have thought, “Kevin thinks about things. He’s a thinker.” He kind of had that moment with William where William’s like, “You doubt yourself a lot.” And then decides to finance the play himself and not quit, which adds another layer, and then he gives the speech to his ex-wife. In the next episode, you see a lot more depth from him and the lengths that he will go to get what he wants. And you see how smart he is -- he’s a very bright guy, he’s just not taken very seriously. If he takes himself seriously, he’s bound by nothing and I think he falls into that trap. I look at him from the moment I met him when I read the pilot to where he’s at now, and it’s a completely different person.

RELATED: 'This Is Us' Reveals When Jack Died -- and Kevin's Shocking Romantic Secret

How much progress do you think he’s made?

I think he’s done a lot in the past few months. We’ve walked along this ride with him, and we’ve laughed and we’ve cried. We’ve seen him making strides even though he stumbles and falls sometimes. He gets up and he continues to go forward. Maybe not at the pace at which he’s used to, which was easy breezy, but he’s also challenging himself with things that are a lot more serious. Look at his relationship with his brother [Randall], his relationship with his sister [Kate], his relationship with Sophie now, where he is with his job. He’s extending and challenging himself, which is kind of nice to see him do. And he’s winning.

Speaking of Sophie, we don’t know much about her at the moment -- only that she grew up with Kevin and became a couple. What is different about Sophie compared to Olivia and Sloane?

When you find your true love, I think it’s easier to explain the feeling -- the feeling that you get when you’re around the person that you truly do love, it’s palpable. You can see it from a distance and I think that’s what Kevin has with Sophie, it’s just a special bond. They grew up together so they have this familiarity that a lot of couples don’t have. For Sloane and Olivia, they were filling a void in Kevin’s heart that they were never going to be able to fill and in his heart of hearts, he knew that. It wasn’t like, “Boy, I’m in love with both girls, which one do I choose?” which is a ridiculous ultimatum he gave himself, which he sometimes does. It’s the feeling that you get when you can’t sleep, can’t eat and all you can do is think about them -- that’s Sophie for him.

We haven’t really seen Kevin’s romantic side. How far does he go to win her back?

Pretty far! He remembers a lot of stuff. Things stick with him and he understands important moments, why they’re important. He paints pictures in his head and he’s very in touch with the finer moments in life and how special they are, and he holds onto those. You definitely see a romantic side coming out in this next episode. You’ll just be like, “Wow, this guy is a romantic. I didn’t realize that.”

RELATED: 'This Is Us' Star Milo Ventimiglia Reveals Jack-Rebecca-Miguel Clue

In an early sneak peek, we see Kevin winning Sophie back with a plate of lava fries, a clear reference to the past. Fair to say we’ll be getting more flashbacks to their childhood and courtship?

Yeah, and we touch more on that. You bring up the childhood and the past, we touch a little more on that and I think it’s going to melt your heart because you’ll be like, “Wow, this guy isn’t saying he’s in love with her… No one remembers stuff like that, how is he doing this? He must have been affected by this girl.”

Is Kevin’s ultimate goal to get back together with Sophie? Is he contemplating marriage again?

It’s to patch things up and try to pick up where they left off. That’s one of the things about Kevin that you realize; when he decided to patch things up with his brother, he’s like, let’s let bygones be bygones, what’s done is done, and we’re good here right? He fails sometimes to realize, or to take into account, the process. Just because you want to be friends with somebody again doesn’t mean it’s going to happen overnight. There’s a healing process and it takes time. He tries to do the same thing with Sophie -- let’s pick up where things left off, let’s get back together, but there are things to talk about. There is dirty laundry to be aired out. It’s not a fun thing, but to sometimes get what you really want, you have to talk about things that are uncomfortable and may be sad, and may be rotten, and things you can’t take back. But sometimes you need closure to open things back up.

Sophie mentions she hadn’t seen Kevin in over a decade, which means they married young and got divorced in their 20s. Is the cause of their split as simple as marrying too young or was it one big event that tipped the scales?

We talk about this very thing that we’re talking about in the next episode. It gets answered in the episode as to what happened and why they broke up. I don’t know that it’s one event, but it’s a series of things that led up to one event where you’re like, OK, this is not going to work. You hear both sides of the story, but we’ll touch on his side and her side as to what happened.

RELATED: 'This Is Us' Renewed for Two More Seasons

Kate is now engaged to Toby, so curious if there comes a moment when Kevin talks to Kate about his past experience or is that its own separate thing?

It’s its own separate thing. We haven’t had anything quite like that yet. All three of them grew up together and it’s a sore subject, as far as Kate is concerned, with Sophie. They were childhood friends and married to her twin brother and then divorced. That’s probably something Kevin’s not going to bring up or she’s going to bring up. (Laughs.)
Are Kate and Sophie still on speaking terms?

There was definitely something that happened in the relationship. It’s a weird thing, right? “I’m your best friend. You married my brother. You got divorced. Are you my best friend anymore? What am I supposed to do, abandon my brother?” It’s tricky.

Knowing now that Jack died when Kevin, Kate and Randall were teenagers, arguably the most pivotal time in a kid’s life when they need their parents the most, how devastating is that for The Big Three?

I love the way that they’re telling that story where he died at that pivotal time when they were 15, 16, 17 years old. There’s so much that you’ve learned from your father at that point in time, but there are so many more things that you would have to discover on your own in different ways somehow if you didn’t have your dad. It’s great for storytelling and it’s great for our show because we’re going to get people to cry a lot. (Laughs.) How did Kevin learn how to date? How did he propose? You’ll definitely see not only his death, but when it happened that will tell little stories as to why his kids act the way they do at certain times. They all have their own guilt and their own version of how it happened.

What sort of emotions should we expect to feel in the final five episodes of the season?

The show may take a dark turn. It may take a dark turn, so get ready for that. It gets real.

What's been the one scene that completely tore you up?

Oh boy. I loved the “Three Sentences” speech Kevin gives to Sophie, and Kevin’s got a speech in the next episode that will probably break me up a little bit when I watch it.

This Is Us airs Tuesdays at 9 p.m. ET/PT on NBC.

PHOTOS: The Cutest 'This Is Us' Cast Snapshots