Why is Bran hiding details from the other Starks?

Question

In "The Dragon and the Wolf" (Game of Thrones, S07E07), Bran told Samwell about the secret of Jon Snow.

That he is a bastard of his aunt Lyanna Stark and Rhaegar Targaryen. Later Samwell explained to him how Jon can't be a bastard.

But why Samwell?

Why is Bran not sharing this information with Sansa? After all, she is his sister and moreover, she is the Lady of Winterfell, for now.

He does not share this detail even with Arya Stark.

What's in his mind to decide not to discuss this important detail with his family?

Answer 1

As others already commented, that info might cause chaos among the lords. But there is no reason to believe that family members can be trusted more than Sam. Actually they shouldn't be trusted at all. It is about heritage and inheritance, and in the game of thrones it is family members that may cause biggest chaos, because everyone is triggered by the idea of power. Even Sansa has to ask Arya after Littlefinger was already dealt with, and even Arya is not immune to idea of ruling. No, Bran is right not to trust other family member on this matter.

Better question is should he have told even Sam. I can see few reasons why he might have chosen to trust Sam, probably Bran greeseered about Sam and Sam also kept secret about Bran until he returned south of the Wall. And Bran probably knows that Sam is the person Jon trusts the most. But why did he told even to Sam, I guess Bran wanted to be sure there is someone else that knows this too in case something happens to him. Or if Jon doesn't make it to Winterfell but must fight somewhere else, Sam is more likely to see Jon than Bran.

So I understand that if Bran wanted someone else to know too, Sam is the only choice, I'm just not sure should he put that kind of trust even on Sam. But family members? In feudal kind of universe? Nooooo way.

Answer 2

What the Three Eyed Raven Says

Bran is clearly somewhat disconnected from reality, in his new role as the Three Eyed Raven. He doesn't really think like normal people do anymore, so it's difficult to assign a normal person's motivations to him. He has demonstrated a propensity for saying as little as possible, but saying it to exactly the right person. He likely waiting to share the fact of Jon's birth with Jon directly, because it really has no bearing on anybody but Jon.

What the Three Eyed Raven Knows

While he theoretically has access to a vast amount of knowledge, it's become clear that he doesn't know everything yet. It's somewhat like having exclusive access to the card catalog in the library - he can look things up, but he has to know to look for them. I suspect over time that he will have better mastery over whatever passes for an "indexing function," but for the time being, he's still new at it.

Bran knew about the birth of Jon, because he had a reason to go looking for that particular information in the "archives" available to the Three Eyed Raven. He didn't know about the wedding because he didn't have a reason to go looking for it. As soon as Sam gave him that reason, he "pulled the file" and viewed the event.

Answer 3

Because that news is a total game-changer, and of such magnitude that no one would keep it secret.

If he shares it with others, what happens to Jon, who is still completely in the dark? He's a Targaryen with the rightful claim to the Iron Throne. They were talking about resentment in the north towards that family and towards Daenerys and how someone might want to take her out because of it. That could very well translate to the same feelings about Jon (who also let wildlings past the Wall). If word gets out and there are spies anywhere, then Cersei knows there's someone with in irrefutable claim that trumps hers, and either assassins or direct attack might come.

In either case, Jon would be completely blind-sided.

There's also considerations of that news fracturing their family unity, with Bran and Sansa now holding the exclusive legitimate Stark succession rights (which they already had, but the lords and Sansa were all willing to align behind Jon because "Ned Stark's blood runs in his veins" - or so they thought). There's considerations of fracturing the Northern and Vale alliance - Jon bent the knee, as King of the North, committing the North, but if people find out he's actually Targaryen, then what he did was pledge the North to himself as the King of the North - a title he gained under, it would be viewed, as suspect circumstances (did he know before?, they might ask).

Finally, Jon has to decide what he wants to do with this information. Is he going to try and claim the Iron Throne for himself? Will he denounce that claim and defer to Daenerys? Will he make an announcement while giving up his claim as King of the North? Anything he wants to do, if he wants to keep things in place to fight the Night King and, eventually Cersei, will have to be considered and thought out. If Bran blabs that to anyone, it's basically blabbing it to everyone. Jon can't plan or think out his options, because the ball will already be in motion, but without any kind of control from Jon.

Basically, if Bran told anyone else but Jon's closest friend who has no motives that would be impacted, except to support Jon (answers "Why Sam?" - even Sansa and Arya are impacted as members of the Stark family), he'd be acting like a major jerk. Jon has to know, first, and then he has to decide what to do with that.