This is one of this mini mysteries that I’ve never quite figured out.
The first time that Robb appears in the story, he’s described as being shorter than the greatsword Ice, as well as Joffrey, who’s two years younger than he is. One would assume that Robb is quite a short person, even if he’s only fourteen, but then later on, Catelyn describes him as being a tall knight on horseback at the Whispering Wood. We can assume the horse adds to his height, or he very well may have had a big growth spurt between the start of the book and the Whispering Wood, or Catelyn is unreliable. I can’t recall if there’s any other mention of Robb’s height in the books, but it’s already confusing enough given the aforementioned examples.
We know that the Starks tend to be average or even short height, but Robb takes more after the Tully family in appearance. I don’t remember Hoster, Brynden, or Edmure’s heights, or even if they’re discussed, but if Robb is an indication, they must not be that tall either.