Who is John from Daughter of the Forest and what is their importance?

John is one of Red's friends and a member of his personal guard. He travels with Red to Ireland in search of Simon, despite the fact that his wife is expecting their second child. John is described as a kind man, who offers unconditional understanding to Jenny from the moment they meet, and his wife, Margery, will become Jenny's only friend while she lives at Harrowfield.