Heavily modify? Maybe add two skills, set goals for members of specific Houses to achieve to earn XP, and set up a method of accounting of actions. I've got a deeply political metaplot going on in my current campaign (Session #28 this week), with less than that. Players can think for themselves; you don't need a dice roll for everything.
Whereas Elf boy either has the too-common Legolas fixation, or he knows nothing about GoT, or didn't like the books. In short, not someone you want in a thinking player's campaign. He needs to find a group that suits his expectations. Hammering a square peg into a round hole is a recipe for failure.
More than simple modify.
Full on class builds or purchasing of books.
Most adventurer fantasy RPGs don't even have the capability to run the noncombatant all skills character most of the female nobles and some male nobles in the book series.