You didn't ask me but I'll tell you what I think. I call bullshit. It doesn't even matter if they are twins, how does that even affect anything? Also, this smug TV blog writes, "Interestingly enough, many of the Stark kids have their ages next to them in subsequent book appendices, as well. Jon Snow's age, however, is conveniently removed, while Meera's age is changed in later books to 16. Could this be because we would notice their ages changing at the same time? Seven hells! That makes sense to us." It takes Martin years and years to write these books, why the fuck would he change shit in between books before the show was even made? Yeah. Total bullshit theory.