It's been 23 years since a little book called A Game of Thrones introduced an angry young kid named Jon Snow to the universe. That poor kid, believing himself to be the byblow of Ned Stark, the patriarch of Winterfell, wanted to close himself off from the world, join the Night's Watch, and never risk fathering a bastard himself. Nearly a quarter century after Ned first promised Jon they'd talk about his mother "one day," Jon Snow learned about his true parentage. He is Aegon Targaryen, but what will happen between Jon and Dany now that they're officially related? Warning: Spoilers for Game of Thrones Season 8 follow.
It took a medium jump from page to screen, a vision and Gilly learning to read, but finally, Sam sat Jon down and told him the truth. Ned Stark was never his father, and Jon was never a bastard. These were stories concocted to protect him. His parents risked not only the wrath of their families, but the entire Seven Kingdoms to have him. They moved heaven, earth, and at least a couple of archmaesters, to procure an annulment for Rhaegar, before marrying so that their son, Aegon Targaryen, the Prince That Was Promised would grow up to save the world.
Ned lied to Jon all those years, but he did it to protect him. If anyone had ever breathed a word of Jon's true origins, it would have put him in immediate danger, most directly from Robert Baratheon himself. Ned knew, for all Robert's protestations of love for Lyanna, he would have killed her son in a heartbeat because it wasn't his.
Fans had thought going in that Bran would be the one to blurt out the news. Instead, it came from Sam, which is the best case scenario. If Jon had to learn everything he knew about his existence, all the way through to his own name, was a lie, best let it come from Sam, his BFF, and one of the few men he trusts with his life. As much as Bran is Jon's brother (well cousin), his transformation into the Three-Eyed Raven makes him too cold and remote for such a news drop.
So it falls to Sam to tell Jon. He's got the motivation when Bran sends him down to the Crypts to tell Jon the truth. Sam has just learned his father and brother were murdered by Daenerys for not bending the knee. In his view, Jon would never do such a thing. In fact, he knows Jon wouldn't. He saw Jon spared Wildlings when they wouldn't kneel.
But then Sam really twists the knife, when Jon tries to back away from being told he's really Aegon VI Targaryen, true King of Westeros.
You gave up your crown to protect your people. Would she do the same?
Jon knows the answer. It's not yes.
The real question, of course, is how everyone else is going to react when this gets out. Jon says Sam's calling Dany not the true queen is treason. But Jon may find there's going to be many more of those saying the same treasonous statement very soon.