Kegger at Robert's

I remember Robert bringing up Dany to Ned in AGoT. It was Ned's POV. I've got it in front of me now. Ned's internal dialogue talked about Tywin presenting the dead Targ children and Robert turned away from them. Referred to them as dragonspawn. Ned called it murder by the Lannister men, Robert called it a casualty of war. Ned also mentioned that Jon Arryn couldn't stop the disagreement. Ned rode south "in a cold rage". It apparently took Lyanna dying to stop the fight. It doesn't say what characters saw the fight. At least Jon Arryn, maybe Tywin. Jon Arryn was the envoy sent Dorne after the rebellion ended and he stopped any immediate retaliation from them. Its possible he mentioned it to Doran Martell, implicated the Lannisters. I think the Kingslayer mentions something about this in one of his POV's. I cant remember.