- Jonah Wizard is one of the Cahills that was a part of the search for The 39 Clues. Jonah is an international rap sensation, and an actor in the series Who Wants to be a Gangsta, having even his own action figure and many other products such as pop-up storybooks, and a Pez container with his face on it, even a frozen treat brand. In the first series, Jonah Wizard dislikes Dan and Amy Cahill, only because they were Grace's favorites. Jonah is one of Amy and Dan's best friends after the Clue Hunt ends.
- Phoenix Wizard is Jonah's twelve-year-old cousin. He gets kidnapped by the Vespers in The Medusa Plot. He escapes by accident in Shatterproof, but lives in the woods until he is found in Day of Doom. While not a famous musician, he is talented with music as seen at the end of Day of Doom. He also is not a huge fan of his cousin's music. While captured by the Vespers he becomes close friends with Nellie Gomez.
- Mr. Wizard is Leila Wizard's husband. He never appears in the books.
- Leila Wizard is Phoenix Wizard's mother and Cora Wizard's sister. She is an inactive Janus who deeply cares about her son. She is married to Mr. Wizard.
- Jonah's mother, Cora Wizard, is the leader of the Janus branch, the youngest ever Nobel Prize winner and has made several sculptures and books, one of which she "donated" to Hope Cahill and Arthur Trent when Dan and Amy were very young, which in fact was an attempt to spy on them with a electronic bug planted on the sculpture. Some consider her almost as evil as Isabel Kabra. She is ruthless, and does everything she can to better the Janus branch. She disowned Jonah after the events of Into the Gauntlet for failng to get the serum for the Janus branch.
- Cora Wizard's husband, Broderick Wizard, was not a born Cahill but joined the family by marriage to Cora. Also, around the time they married, he was an excellent guitarist and a rising star in his college days, however compared to other Janus, he seemed amateur. Because he is not a Janus by blood, however, he sometimes only has limited access to the Janus branch, as seen in the Janus stronghold in Venice. Naturally, this annoys him a bit. He can always be found on his BlackBerry. After the events of Into the Gauntlet he chose his relationship with his son over his relationship with his wife. It is unknown if he and Cora Wizard are still together. He was strongly suspected as a Vesper, but fortunately he wasn't.
- Broderick T. Wizard - Married into Cahill family, suspected Vesper, Cora's husband, Jonah's father, Mr. Wizard's elder brother, Leila's brother-in-law, Phoenix's uncle.
- Cora Wizard - Head of Janus Branch, Broderick's wife, Jonah's mother, Mr. Wizard and Leila's sister-in-law, Phoenix's aunt (Wizard family by marriage)
- Jonah Wizard - Broderick and Cora's son, Mr. Wizard and Leila's nephew, Phoenix's cousin.
- Mr. Wizard - Minor character, Cora's brother-in-law, Jonah's uncle, Leila's husband, Phoenix's father.
- Leila Wizard - Cora Wizard's sister, Broderick's sister-in-law, Jonah's aunt, Mr. Wizard's wife, Phoenix's mother
- Phoenix Wizard - Broderick and Cora's nephew, Jonah's cousin, Mr. Wizard and Leila's son. Kidnapped by Vespers in The Medusa Plot.
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