'This Is Us' season 1 episode 13 spoilers: Jack and Rebecca throw separate parties for the triplets; upcoming episodes to explore Miguel's backstory

Jack (Milo Ventimiglia) and Rebecca (Mandy Moore) prepare for the triplets' birthday on the upcoming episode of NBC's family drama "This Is Us" season 1.

Titled "Three Sentences," next week's episode centers on the triplets' special day. According to the official synopsis, Jack and Rebecca are stressed out when they decide to throw Kate (Mackenzie Hancsicsak), Randall (Lonnie Chavis), and Kevin (Parker Bates) three separate parties for their 10th birthday.

Meanwhile, in the present, Randall (Sterling K. Brown) finds it difficult to make time for William (Ron Cephas Jones) as things begin to intensify in the office. Kevin (Justin Hartley) is forced to make a major decision in his romantic life, while Kate's (Chrissy Metz) gastric bypass surgery takes a surprising turn.

This week's "This Is Us" featured a tear-jerking standalone episode going all the way back to when Rebecca was still pregnant. After forgetting her husband's birthday, she kicked him out of the house to spend some alone time. The plot also dealt with the history of Dr. K (Gerald McRaney) and of the firefighter (Brian Oblak) who brought Randall to the hospital when he was a baby.

Aside from Dr. K and the firefighter, fans are also looking forward to knowing Miguel's (Jon Huertas) background. Known as Jack's best friend, Miguel later on married Rebecca after Jack's death. Showrunner Dan Fogelman recently caught up with The Hollywood Reporter, and he assured fans that more episodes featuring Miguel will be aired soon.

"We're getting a lot of Miguel coming up actually. I'm editing right now and I'm editing a ton of Miguel in upcoming episodes," Fogelman said. "You're going to learn a lot more about Miguel, about his relationship with Jack, about his own marriage. So yes. There's a lot of Miguel stuff coming," he added.

The first season of "This Is Us" airs every Tuesday night at 9 p.m. ET on NBC.