Who is Garrick Courtney from When the Lion Feeds and what is their importance?

Garrick is Sean's twin brother, and the milder of the two. Slim of build, Garry's wrists and ankles are much like those of a girl's. He is freckle-faced, with pale blue eyes and hair that grows wispy and brown. He suffers from constant hay-fever, giving his eyes a slightly pink look. He defers often to his brothers stronger personality, and loses a leg as a result. This accident shapes the rest of his life.