Grace Cahill's branch of the Cahill Family is a member of the broader Cahill Family. Most of the blood family members belong to the Madrigal branch, though the family also has Lucian history (diluted over the generations), and some Ekaterina heritage mixed in to later generations. Though Grace was not the oldest member of the section of the family, she was one of the most influential members of the branch, and the wider Cahill family. Other notable members of the family branch include Dan and Amy Cahill, Grace's grandchildren, who won the Clue Hunt.
- Dan Cahill - Main Protagonist.
- Amy Cahill - Main Protagonist.
- Hope Cahill - Dan and Amy's mother (deceased)
- Arthur Trent - Dan and Amy's father (deceased)(married into the famil)
- Grace Cahill - Dan and Amy's grandmother (deceased)
- Nathaniel Hartford - Dan and Amy's grandfather(deceased)
- Beatrice Cahill - Dan and Amy's great-aunt (deceased)
- Fiske Cahill - Dan and Amy's great-uncle and guardian
- James Cahill - Dan and Amy's great-grandfather (deceased)
- Edith Cahill - Dan and Amy's great-grandmother (deceased) (married into the family)