I was trying to be humorous, I guess in writing it didn't come across as that.

But if you wanna talk about it seriously, I'm sure he thinks about lots of stuff, POV characters are usually wrong in their assumptions though. I could mention that Cat thought Ashara was Jon's mother, but my previous argument already undermines it I guess. Still, Ned was the only Stark who seemed to be interested in her. Regardless of who the father is, if the resulting baby was indeed Jon, it would explain why the Daynes think Ned is so awesome (to the point of Ned Dayne being a thing), despite Ashara committing suicide as a result of the whole situation.

Lyanna might have given birth to someone else.

Sure, R+L=J has a lot of evidence, and it's probably right, I just hate people treating it like it's already canon, and condemning all other theories as blasphemy.