"While there's going to be tough times ahead, this family, whatever happens in the future, finds its way back to one another," the actor tells PEOPLE

WARNING: This post contains spoilers from Tuesday’s episode of This Is Us.

After the Big Three (a.k.a. the Sad Three) had one hell of a week, they reunited at the Pearson cabin to unwind on this week’s This Is Us.

In the present day, Kevin (Justin Hartley), Kate (Chrissy Metz) and Randall (Sterling K. Brown) retreated to their family vacation home after their recent dramas: sleeping with his sister’s best friend, dealing with her husband’s distant relationship with blind son Jack, and coming to terms with his anxiety, respectively.

And there were a couple of secrets that came out — specifically, Kevin finally finding out about their mother Rebecca’s (Mandy Moore) ailing health. The matriarch had made Randall and Kate promise to keep the diagnosis to themselves as Kevin deals with his sobriety amid feelings for his ex-fiancée Sophie. But behind Kevin’s back, Randall had already made a secret trip to Los Angeles to meet with a specialist about cognitive impairment.

Meanwhile, the show flashed back to the Big Three’s teenage years, as Rebecca led a rescue mission with her sons to the cabin where Kate (Hannah Zeile) and boyfriend Marc (Austin Abrams) had a verbal fight during which he once again fat-shamed her. Even worse, after he destroyed her father Jack’s (Milo Ventimiglia) “world’s greatest dad” cup, he locked her out in the freezing cold, which led her to injure her hand breaking a glass window.

Credit: Ron Batzdorff/NBC

Going back even more years, the young Pearson family chose sentimental items to bury in a time capsule. The original plan was to dig up the container five years later, but Jack died before he would ever find out what his loved ones had included. For his contribution, the patriarch recorded a cassette tape that chronicled the special day’s play-by-play, including how Rebecca saved her husband’s sketch of the dream home he hoped to build near the cabin.

Then, in the tear-jerking cliffhanger, viewers saw Kevin take his father’s drawing in the hopes of building it on the same property. Fast forward to the future, the actor (in aging prosthetics!) returned to the Jack-inspired cabin with take-out in-hand as Beth (Susan Kelechi Watson) told him that the family, as well as Kevin’s son, was with Rebecca, presumably in hospice.

Audiences will remember how the flash-forward scene was first introduced in the season 3 finale when the core cast gathered at the house, where Kate’s husband Toby (Chris Sullivan) arrived alone and without his wedding ring.

Though the episode evoked feel-good cabin memories between the Big Three, we saw, earlier this season, that the cabin will also be the location where the siblings come together for their forthcoming 40th birthday party when Kevin and Randall aren’t on speaking terms.

This is Us
Credit: Ron Batzdorff/NBC

“There’s harmony to come from the siblings, from these two brothers. But that’s what makes the fact that you know they’re not speaking to each other within a year all the more heartbreaking,” Brown, 43, tells PEOPLE. “And you’ll see, that kind of plays itself out during the finale of the season.”

But before fans witness what exactly went down between the brothers, Brown teases that “there are good times to come” before the conflict.

“Even in the past, you can see there are times in which Kevin treats Randall like a total douche and then there are times in which Kevin is a total rockstar,” he says. “It’s just sort of the nature of Kevin. He’s been incredibly charming, so supportive, so romantic and then just so selfish and self-absorbed.”

Brown further foreshadows, “We know in the ultimate future we are at Kevin’s house when we see Rebecca and we see Kevin’s son, so we know that, while there’s going to be tough times ahead, this family, whatever happens in the future, finds its way back to one another. In the course of the show, you will see the light and the dark, but you will always finish in the light, always.”

This Is Us airs Tuesdays (9 p.m. ET) on NBC.