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human
[Game of Thrones] Could Robb have declared Jon a Stark when he was King of the North?

When Robb became King of the North, would he have the ability, as King and head of the Stark House, have the power to allow Jon to be a Stark or was Ned the only one capable of doing so?
gpt
Yes.  A king can legitimize any bastard. This would have presented problems for Robb however. The king doesn't declare a person a member of a house he legitimizes bastards, saying that a person was born with all rights a privileges as if his parents were married.  Legitimizing Jon as Ned's son might place Jon as first in line not Robb. There is some question of which is older though that should be able to be settled now.

Catylan says: If you make Jon legitimate, there is no way to turn him bastard again. Should he wed and breed, any sons you may have by Jeyne will never be safe.”

If Jon is the eldest son of Ned then Robb does not have a claim to be the head of the Stark family its Jon's place. While Jon might not press the claim his children might press it on Robb's children.  Since at the time its not clear when/where Jon was born there will always be some question of which was older.  Robb would not take the chance of doing this unless it was clear he would die without heirs (including Brandon and Rickon) and needed Jon to be legitimate in order to perpetuate the Stark line.