Angelcest

Castiel and Anna in 4.16. 'On the Head of a Pin'

Angelcest is the commonly used term for Fanfiction focussing involving angels in a sexual relationship.

The term can be used for both slash and het pairings.

Its use arises from the convention of angels referring to each other as 'brother' or 'sister'. Angelcest is not often considered as not-analogous to human incest by the fandom, since the angels are possessing vessels and them being brothers and sisters can be interpreted differently from the terms used for humans.

Angelcest often involves a metaphysical level of sexuality in fanfictions, that involves the connnection or sharing of grace.

Common angelcest pairings are e.g. Anna/Castiel or Castiel/Gabriel.

See also Wingcest