This Is Us Boss Breaks Down That 'Brutal' Fight and Addresses Kevin's Fiancee Mystery

[Warning: The following contains spoilers from the Season 4 finale of This Is Us. Read at your own risk!]

This Is Usfans were taken on yet another emotional rollercoaster in Tuesday's Season 4 finale, which answered a lot of the season's biggest questions -- we know who Kevin's (Justin Hartley) baby mama is! -- but also left us with a few more quandaries about what's to come in Season 5.

First things first, the mother of Kevin's children (yes, multiple) is Madison (Caitlin Thompson), who discovered she got pregnant from her one-night stand with Kevin after his trip to Pittsburgh. And she's not just pregnant with one kid, but twins. Those Pearson multiple-baby genes run strong! However, Madison decided to tell Kevin about his unborn children at exactly the wrong time, just as he and Randall (Sterling K. Brown) were really getting into it over Randall guilt-tripping Rebecca (Mandy Moore) into going to St. Louis for the Alzheimer's clinical trial.

The fight left no doubt as to why the brothers weren't speaking on their 40th birthday in the fall finale's flash-forward scene. It was a no holds barred verbal altercation on Kate's (Chrissy Metz) front lawn after Kevin found out what Randall did. When Kevin accused his adopted brother of having a failed hero complex, Randall rubbed it in that Jack (Milo Ventimiglia) died ashamed of the eldest of the Big 3. Kevin rebutted with the fact that the worst thing that ever happened to him was Jack and Rebecca bringing Randall home from the hospital. It still hurts, you guys.

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Though the two ended on the worst possible terms in the present timeline, they seem to be friendly enough in the last flash-forward to Rebecca's hospital bed in the new cabin in the future, where we learned that Kevin and Madison's twins are a boy and girl. Beyond that, the finale also showed adult baby Jack (Blake Stadnik) welcoming his first child into the world and revealed that Toby (Chris Sullivan) and Kate adopt a little girl as well. There was some good news to come out of all of this, at least.

However, even knowing who Kevin ends up with and what led him and Randall to stop talking, there are still a lot of burning questions left. What does this fight mean for Randall in the immediate future? Will Rebecca still go to St. Louis? Do Madison and Kevin actually get married? TV Guide was part of a small group of journalists who got to ask This Is Us creator Dan Fogelman about the big events of the episode, and what they'll mean for Season 5.

Can you confirm that Madison is Kevin's fiancee?
Dan Fogelman: I believe there's an immediate answer coming to all of that, but I think that there's basically a lot more...many more chapters in Kevin's romantic story. We are far advanced already. I've already written the season premiere of next year and broken, I think, five episodes of the season, and we have mapped out plans for the entire next and sixth season honestly, so Kevin has a journey ahead of him, and I don't want to get too far ahead of it just yet.

What can you say about his statement that the twins would be the love of his life?
Fogelman: It felt like an interesting time to have a character embark upon parenthood, and embark upon becoming a parent with somebody who's a virtual stranger to him. [It is] a different kind -- potentially-- of story between a man and woman who are raising a child together.

Can you talk about writing the fight between Kevin and Randall, and figuring out exactly how mean they'd be to each other?
Fogelman: So we've been working for a while. I think it's been carefully baked into both the show at large and the season, and the last half of the season, specifically. This is a fight that goes -- this is Cain and Abel type stuff for these two. This is a fight that goes, you know, towards, literally, their inception; Two kind of alpha men growing up under the same roof with the exact same period of time, both with two wildly different skill sets.

It's easy to forget now, 70 episodes into the show, but these two brothers have only really gotten along, and had a real adult relationship for the two and a half, three seasons of the show. When we first met them, until halfway through Season 1, these brothers felt very estranged. They often weren't that close and developed this relationship over the course of the first couple of seasons. So, it didn't take a lot to bring them back to their kind of primal wounds, and pull them apart. These aren't brothers who have been kind of speaking on the phone every day...All of that kind of fed into what we tried to execute. It just felt like the guys [were] so brutal, and [acted] so brilliantly. Obviously, it's all done in one take. I think part of part of making a drama, part of making a human sub-drama, is not being afraid to let people be really flawed and really ugly. So that hopefully, as we tend to do on our show, offer the kind of hope we offer and the repair we might offer is well earned, and well executed when it comes.

What does Randall's 40th birthday look like in the wake of this fight and the fact the Pearsons will be with Kevin?
Fogelman: I've just been writing it. I think that Randall, without being the center of this extended family and having this kind of fallout with his brother who he's gotten close with -- maybe it can be fair to say the immediate family, the family that he lives every day, that would become something he would hold incredibly tight. His 40th birthday, it's not just him sitting on the couch eating Cheetos and crying the entire time. I think it's fair to say there's a longing, but also the immediate family rallying around him is going to try and make it all work.

Rebecca is not willingly going to this trial in St. Louis. What can you say about how this experience is going to play out for her?
Fogelman: It's obviously a challenging chapter for Rebecca, moving forward. We have a big storyline planned for Mandy in the next upcoming season in present day, as an older woman, and also her past timelines. Particularly, it's an opportunity for us when we land in St. Louis with her [and] Miguel. So often they operate as a couple in service of the larger family. When you see them together, it's because the entire family's there and has storylines. But here's an opportunity where we're going to be joining them in a location together, kind of, together, as they kind of undergo this [journey] that they didn't necessarily plan on trying. And that will also allow us to kind of get towards -- which has always been the plan in the back part of our series -- get towards a further understanding of how their relationship bloomed, then stalled, then kind of bloomed again, and getting really inside of their lives.

You cast Adelaide Kane as Kate and Toby's future daughter. Can you say if we'll see her in Season 5, and will there be more of a shift towards the future flash-forwards instead of the flashbacks now as we get invested in those characters?
Fogelman: We really love the actress we found to play the daughter, Adelaide as you said, and obviously we've really [fallen in love with] Blake, who plays Jack Jr. as a character. So our hope is to continue to make people invested in these future storylines by getting into the characters slowly, as we've done, so that by the time you're really landing in full stories with them, if we do, you feel that great investment. In terms of the balance between the future storylines and the past...We've parsed out the shape enough that we will never run out of the past flashbacks that inform the present. Milo will always be in the show, Young Rebecca and younger versions of the kids will always be in the show. But we do the plan is to kind of tilt into different timelines that go past our present day a little bit more as we move forward. And more of that is coming, and not just in that deep, deep future where Jack Jr. lives.

As a follow-up, will Seasons 5 and 6 have more of the Big 3's children? Understanding there are a lot of characters to balance, but will there be more Deja and Tess, etc?
Fogelman: We have a plan for all that. I think by the time the Pearsons' story kind of wraps up on our series, you'll have gotten to have a lot of not just answers, but a lot of check-ins to figure out and understand where everyone's characters are in the big wide span of their lives, and that includes the children. It's always so interesting to look at the matriarch and patriarch of a family like Jack and Rebecca [and see them] simply on a bed with Milo sitting with a Terrible Towel covering up his junk, and then realize that decades later there will be all these human beings that are offshoots of these people, both biologically and emotionally through adoption, and that family tree and the growth of the family tree and doing it in this really elegant and slow way where, you know, we started with a guy and a girl on the bed and we ended with this giant kind of fabric of life is something we've always hoped to execute by the time we're done.

We saw that Nicky is married in the flash-forward. Can you say whether we've already met his or Kevin's future wife?
Fogelman: It's a good question. I'm like frozen like a presidential candidate on the debate. How do I answer that question because either answer would kind of give too much away. I can safely -- no, I can't answer that.

This Is Us will return for Season 5 in the next TV season on NBC.