Xander is an angel who criticises humanity. I think he calls us 'talking apes'. His punishment is to be sent to Earth to live as Tony and Jessica Harris's son and learn what it is to be human. As an extra punishment he remembers being angelic but has none of his powers.
He has an angel 'friend' who may or may not be Gabriel.
He hooks up with Spike and somehow Angel and Wes (possibly others) become involved in a mission to save an orphanage of Demon or half-Demon children. I remember they have to wear 'glamours' to hide their identity.
It's an older fic. Ring any bells?