Nah, ALL the characters are younger in the books than they are in the show. By a couple years I believe.
Dany is 13 in the start of the books. Pretty sure Robb was 14, Jon Snow was 14. Arya is 9. Bran was 10.
In this world, kids mature much faster and it's not uncommon for kids to assume the roles of an adult much sooner in life.
Robb is like 15 or 16 when he is proclaimed King of the North and starts commanding troops and kicking Tywin's ass.