'This Is Us' Season 3: What Will Happen on NBC Premiere Episode?

This Is Us Season 3 is set to premiere on NBC on Tuesday night.

The drama series will unveil more about the Pearson family's past and where they're headed. The premiere episode will center on the Pearson children Randall (Sterling K. Brown), Kevin (Justin Hartley) and Kate (Chrissy Metz), all of whom will be celebrating their 38th birthday when the first Season 3 episode begins.

The sneak peek trailer for the premiere episode teased trouble on the horizon for Kevin and love interest Zoe (Melanie Liburd), the cousin of Randall's wife Beth (Susan Kelechi Watson). Kevin and Zoe's love connection was revealed in a flashforward scene back during Season 2. In the Season 3 opener, Beth will confront her husband about it.

"Now I'm sure of it. Your brother and my cousin are knocking boots," Beth says in the clip.

Randall appears to be clueless about the matter and makes Beth swear on Oprah not to make a deal out of it at the sibling's 38th birthday celebration. Beth obliges but whispers, "Even Gayle lets Oprah down sometimes."

Throughout the season fans should expect to learn more about Randall and Beth's romance and how they met. In a summer interview with Variety, Brown revealed Season 3 would "explore a little bit about the past relationship between Beth and Randall and how they came into each other's lives."

Beth and Randall's meet-cute won't be the only topic covered on Season 3. After Season 2 finally revealed family patriarch Jack Pearson's (Milo Ventimilglia) tragic death by house fire, Season 3 is slated to feature even more glimpses into Jack's past, including how he and Rebecca (Mandy Moore) came to be. Ventimiglia revealed to Variety fans will get to see more of the couple's younger days before their children came into the picture.

"Script to script, I'm learning the little things, the little moments that collectively make up the larger pieces of who Jack is in whatever time we're discussing—whether it's Vietnam and his experience there and for the audience learning about his brother or maybe an early courtship of Jack and Rebecca," Ventimiglia said in August."

The new season will also unveil more of Jack's time in the military during the Vietnam War.

Jack's Vietnam history was briefly discussed in Season 2, during which fans learned he had a brother Nicky who also served alongside him. Though thought to be dead, Season 3 will offer more details on Jack's brother and will include more glimpses of him. During the summer NBC revealed actor Michael Angarano signed on to play Nicky.

As for Kate and her new husband Toby (Chris Sullivan), the newlywed's storyline will feature more insight on Toby's family. Toby's parents, played by Dan Lauria and Wendy Malick, were introduced in the Season 2 wedding finale but his estranged brother was missing in action. According to executive producer Elizabeth Berger, Season 3 will reveal more about Toby's family ties.

"Obviously, it's such an estranged relationship that he didn't even bother to come to Toby's wedding," Berger told Entertainment Weekly in August."And moving forward as we get to know Toby better in season three, we're definitely going to be exploring his family and his relationships in a deeper way."

This Is Us Season 3 premiere on NBC at 9 p.m. ET on Tuesday.