On This Is Us, flashbacks showed Jack Pearson taking Randall and Kevin on a boys camping trip and, after Kevin pulled a not-so-nice prank on Randall, Jack needed to pull Kevin aside to have a little chat about how important brotherhood is. "Do you think that's funny?" Jack asked Kevin, who asked back, "If I said yes, would you be mad?" Jack then told Kevin, "He's your brother, Kevin. You should be able to depend on each other more than anyone else, more than anyone else in the world. Look at me. You will be good to your brother."
Meanwhile, back at home, Rebecca got a call that Jack's father was dying. So, she radioed the news over to Jack, which caused him to remember his childhood. Specifically, a scene in which his father drove him to a bar and, while a young Jack waited in the car, his father got drunk in a bar.
At the end of the episode, a major plot point was dropped about the original Pearson family, which made Jack's insistence that Kevin be nice to Randall make even more sense. Jack had a brother! In the same flashback of his dad drinking in the bar, another young boy with glasses suddenly sat up in the backseat of the car asking, "Where are we? Where's Dad?" Jack tells his brother, "Don't worry, Nicky, I'm not going anywhere."
This Is Us then flashbacked to Jack, after coming home from the camping trip with the boys, rummaging through some old pictures revealing that his brother Nicky also served with him in Vietnam.
Now, we have so many questions! Where did he go? Is he still alive? Is he as hot as Jack? Looks like we'll just have to wait to find out.