The fans of the books and the show are usually judge Eddard Stark unfairly when they say the length of time it took him to grasp the truth of Joffrey’s parentage shows he’s stupid or unintelligent, are wrong. There, I said it.
These fans are actually betraying their own ignorance of genetics. Consider the following facts: Robert Baratheon has three children who all look like their mother…and so does Eddard Stark. Should we then presume that Catelyn Stark has been schtupping Edmure?