Who is Jojen Reed from A Storm of Swords and what is their importance?

Jojen Reed from A Storm of Swords is from the wetlands. He and his sister, Meera, came to Winterfell for the harvest festival. However, they stayed afterward to be close to Bran, whom they had befriended. Jojen has 'green' dreams, which are something like Bran's dreams where he is inside his Dire Wolf seeing things through the eyes of his wolf.