No, unless they aren't actually siblings.
Amy and Dan are Madrigals. The Madrigals decended from Madeline Cahill. Olivia Cahill (the original cahill) was pregnant with her when Olivia died. Madeline then decided to carry out her mother's wishes. Madrigals try to keep the other branches from finding all the 39 clues. Hope this helps! :)
Amy and Dan are siblings. Amy loves Dan as a sibling and a brother.
Amy and Dan are part of the Cahill family, a secret society in The 39 Clues series. They belong to the Madrigal branch of the Cahill family, one of the most secretive and enigmatic branches.
In Book Seven: The Viper's Nest: Amy and Dan Cahill figure out they are Madrigals
i believe Amy and Dan are Madrigals.
Amy and dan are madrigals, the man in black is their great-uncle, fiske cahill, Nallie is a madrigal too, and Fiske and nellie are the new legal guardians of Amy and dan.
In the book THE VIPER'S NEST it reveals the Dan and Amy are Madrigals.
Ashley Jackson will play Amy Cahill. Adam Hicks will play Dan Cahill.
Hope Cahill and Arthur Trent
The older sister of Dan Cahill.
The man in black is Fiske Cahill, who happened to be the brother of both Grace and Beatrice Cahill. In book 9 Fiske Cahill explains to Dan and Amy that the madrigals try to bring peace to all the other branches. Then Amy and Dan realize they aren't on the bad side. Fiske explains that he didn't want to participate in the hunt but just before she died grace asked Fiske to watch over Dan and Amy.
Ashley Jackson plays Amy Cahill. Adam Hicks plays Dan Cahill.