The Blackthorn family is an old and wealthy Shadowhunter family.
In 1878, Rupert Blackthorn married Tatiana Lightwood. Months before the birth of their first child, Jesse, Rupert was eaten by a demonic worm that was once Benedict Lightwood. Despite Rupert's death, Tatiana was still taken in by the Blackthorns.
As of 2012, the Los Angeles Institute is run by a Blackthorn and has been since as early as 1993. This generation of Blackthorns has a little bit of faerie blood, particularly in Andrew's eldest children, Helen and Mark, whose mother was a Seelie Court lady named Nerissa. This family is notable for their blue-green eyes and their names based from Greek or Latin historical figures because of Andrew's fascination with their mythology.
The symbol of the Blackthorn family is a wreath of thorns.
Other known Blackthorns whose lineages are unknown:
- There was originally set to be eight Blackthorn children in Julian's generation. A character named Ariadne Blackthorn, who was set to be the eighth and youngest Blackthorn, born in 2007 in the series and part of the original planned characters for The Dark Artifices, was written off during the writing of City of Heavenly Fire "because she wasn't working with the plot structure," and because there were already too many Blackthorns. Because of this, previous statements made by Helen in City of Lost Souls and Sebastian Morgenstern in A Dark Transformation, stating that there were eight Blackthorn children, have been redacted and corrected in later editions.