In the final moments of this year's This Is Us midseason finale, a huge twist hit viewers, confirming suspicions that Jack's time in Vietnam might not have ended how they thought. Kevin, while visiting Vietnam, was told that his Uncle Nicky didn't die in the war, after all. Then Nicky was shown in present-day, shrouded in shadows, living alone in a Pennsylvania house and still receiving mail under his name. There are so many questions spawning from this development, but one big one could have lasting consequences — did Rebecca know Nicky was alive on This Is Us?
Rebecca has kept secrets from the family before — most notably the information that she was in contact with Randall's birth father. It caused a serious rift in their relationship, and her regret surrounding the situation was obvious. So at first, it feels unlikely that she'd keep another huge secret like this under her belt, especially as this is one that would affect all the children, not just one.
But, as some people have speculated, there's the possibility that whatever happened in Vietnam put Jack and Nicky at odds for life, meaning that Rebecca might be hesitant to ever introduce him into her family dynamic.
The midseason finale ended with a flashback in Vietnam, in which Nicky was missing and an explosion was heard in the distance. Some fans have speculated that the explosion is a result of Nicky doing something unforgivable — he's been seen as bitter and antagonistic toward Vietnamese villagers after what he's experienced in the war, and there are theories floating around that he ends up killing innocent people.
"My gut says Nicky took someone on the boat — potentially the woman in the pictures who gave Jack the necklace — and blew the boat up/killed them. He ended up alive," wrote one Reddit user, SVW1986, adding that this would likely lead to Jack disowning his brother. "Nicky goes to jail, Jack loses his brother despite his best efforts, and the two stop talking, thus, Nicky's dead to Jack."
That scenario definitely makes more sense than another fan theory that suggests Nicky faked his death, leading Jack to believe he was no longer alive. If he faked his death, it seems unlikely that he'd still be using his real name on mail, or that there wouldn't be a Nick Pearson on the list of those killed in Vietnam.
Even if the theory surrounding Nicky's potential crimes proves to be true, and even if Jack did tell Rebecca all about disowning his brother, Rebecca still might not be thrilled with welcoming an actual murderer into her children's lives. She always has the urge to protect her children, sometimes to a fault, and sullying their father's memory with the arrival of an uncle Jack couldn't even bring himself to speak to probably wouldn't be high on her list of priorities. If Jack made the choice to exclude Nicky from their family, it feels like Rebecca would honor that wish long after Jack's death.
Alternatively, Rebecca may not know anything about Nicky at all. As he's shown time and time again, Jack had a habit of lying about everything to do with the war — he insisted that he was simply a mechanic, not an active duty combat soldier, and usually shut down any attempt to dig deeper into what happened to him. If Nicky's actions caused great pain in an already traumatic part of Jack's life, it may have been easier for him to tell Rebecca that Nicky was dead rather than explain the truth.
There are certainly more theories about why Nicky is living a lonely life in the show's present-day timeline. Some speculate that he and Jack were still in contact after the war, but that Nicky eventually pushed him away and refused help Jack tried to offer, leading Jack and Rebecca to leave him in the past. Others think that Jack truly always believed his brother was dead, and by extension, so did Rebecca, and that Kevin will be the one to figure out the truth once and for all.
It seemed impossible for This Is Us to follow up the since-solved mystery of Jack's death with another plotline equally as intriguing to fans, but the question of Nicky's fate comes close. For now, viewers will continue to try and piece together the clues until the most mysterious Pearson finally comes out of the shadows to tell his story.