Heroic heir in DxD

High school student? Check. Heir to a human organization that deals with the Supernatural: Also check. Young Castiel Emiya, son of Shirou Emiya, lives what some might consider a double life. Involved with the supernatural since birth, how would he affect the world of DxD? Let's find out! (DxD fic with multiple elements and characters from other stories, slight bashing on the start)