He is a bastard born of INCEST.
Game of Thrones Season 4, Episode 6
Fornication, treason, INCEST,
the murder of King Robert.
Game of Thrones Season 5, Episode 8
"the boy Joffrey, the boy Tommen,
and the girl Myrcella being born of INCEST
Game of Thrones Season 2, Episode 1
and we're surprised
when the fruit of their INCEST is rotten?
Game of Thrones Season 2, Episode 5
the product of INCEST?
Game of Thrones Season 4, Episode 6