re: Crackpot ASOIAF Theories SPOILERS

While I fully believe that Jon is the child of Rhaegar and Lyanna, I will acknowledge that there is a possibility that his parents could be other people. Benjen Stark is definitely not one of those possibilities. Benjen was the Stark that remained in Winterfell during Robert's rebellion. Lord Rickard and Brandon were both dead. Eddard and Benjen were the only two left. Brandon didn't have any kids (that we know of), and Ned had just stepped in for his brother and married Catelyn. There was no guarantee that he impregnated her on their wedding night, and certainly no guarantee that they would have a son. Benjen Stark was purposely left in Winterfell so that there would always be a Stark in Winterfell in case Ned died in combat. Seeing as how Ned came back north with Jon (to where Benjen was during the entire reballion), then it isn't possible that Benjen is Jon's father.