Board Thread:TV Show Discussion/@comment-29740399-20161026202030/@comment-29740399-20161028133510

Maester Joseph wrote: If Ned told Cat that Jon was Lyanna's son, she'd figure out who the father was. Everybody knew that Lyanna and Rhaegar went south together. (Just not whether it was a kidnapping, or an affair.)

So Ned's decision was "tell all" vs. "tell nothing". I'd guess that the deathbed promise Lyanna extracted from Ned was to never reveal Jon's father.

Yes, this was rough on both Cat, and Jon. The best way to protect a secret is to tell no one; Ned stuck to that policy. The secret survived Ned's death, and Cat's death. (Jon's death, too, but that was temporary.)

Cat's hostility to "Ned's bastard" helped to make the cover story seamless. You're right in that she probably could have guessed the father. Was she at the tourney with the winter roses? Even so she would have heard the story. Well, maybe she heard the "rape" story like the rest of the Starks and wouldn't think he was the father. Not that pregnancy can't come from rape but Lyanna wouldn't be so keen on keeping a baby conceived from rape. I think he could have trusted Cat with the secret. Not told Jon anything though.

Except @GoT Dawn is right! He should have told Jon about his mother by age 12 or so.

But back to Cat. She certainly could have held him in her heart as her nephew and not had the hatered for him and what Ned supposedly did. That about killed her when he came home with a baby and she had baby Rob!