The Blackthorn family is a fictional family from the popular book series The Mortal Instruments by Cassandra Clare. They are known for their strong ties to the Shadow World, a hidden realm filled with supernatural beings like Shadowhunters and Downworlders. The family is particularly notable for their complex relationships and the challenges they face in a world filled with danger. Key members of the Blackthorn family include Jules Blackthorn, the eldest sibling, and Tiberius Blackthorn, who plays a significant role in the family's story. The family's dynamics are explored throughout the series, highlighting themes of loyalty, love, and sacrifice in the face of adversity.