did have a bastard. I think he was too honourable not to tell Catelyn as I do believe he would have told his family in s1 - if given the chance. He was I believe looking for the right time for Jon's parentage to come to light - which was ideally when he found Robert had no heirs. As R+L=J. But I do think Ned had a bastard of his own, Robert made too much of a point mentioning it and Ned didn't want to discuss it. But as Barristan Selmy pointed out, Ned was in love with Ashara Dayne and that her baby girl died causing her to committ suicide. I can't help but wonder if that WAS Ned's baby and as to the reason for Ned's telling Cat might be because of the guilts