[The following contains spoilers for Tuesday's episode of This Is Us. Read at your own risk!]
According to the flashbacks Kate (Chrissy Metz) has to the tragic day of Jack's funeral, the Big 3 are only teenagers when their father passes away. The final shot of the episode shows Randall, Kevin and Kate as their teenage selves standing with Rebecca (Mandy Moore) as a priest presides over Jack's memorial.
That answers one of the big mysteries surrounding how Jack passed away, though Kate's initial reveal that Jack had died implied that her father had still been around for her to watch football with as late as 2006. It's clear now that Jack passed away long before then and Kate watching Steelers games with her father's urn is a longer tradition than anyone thought.
The reveal also confirms that Jack never saw Randall (Sterling K. Brown) or Kevin (Justin Hartley) get married (another truth bomb in this episode was the fact that Kevin was previously married to Kate's childhood best friend). He never saw the Big 3 graduate college or the birth of his grandchildren. He died with a full head of dark hair and his statement mustache.
The fact that Jack died when all of his kids were still teenagers also reinforces the profound impact his loss is for each of them. Now that this crucial piece of information has come to light, the show can dig into how losing a parent at such a young age has contributed to how Randall, Kevin and Kate all turned into the people they are. We can already tell that Jack's death was a significant factor in Kate gaining all of the weight that she's picked up. It remains to be seen how Randall and Kevin were fundamentally changed by the huge event.
There's plenty of time to get into those details though, as Mandy Moore tells TVGuide.com how Jack dies won't be revealed for a, "long, long time" — and the show officially has two more seasons to dangle fans on that rope.
This Is Us airs Tuesdays at 9/8c on NBC.