The Kingdom of Gods by N.K. Jemisin (2011) Orbit

In which Sieh’s story is told – he is the oldest of the Gods’ children, a trickster and in love with a mortal brother and sister – and when they mix their blood in a ceremony as children, Sieh becomes increasingly mortal.  The sister is the heir of the powerful family that rules the world.  Her brother, an inconvenience is sent away to learn how to be a scrivener.  But they are not ordinary mortal children.  They are also the grandchildren of a godling, which makes them demons and makes their blood poisonous to gods and godlings.  While The Three have exiled one of their own, the parallels between the two sets tells potentially the same story.