Like McManus’s other popular works, The Cousins is centered on the power of secrets. Secrets are intertwined throughout the plot to drive the mystery of the Story family. McManus also uses secrets to demonstrate how secrets can drive people apart, but strangely enough, they can also bring people together in unexpected ways.

Upon their first meeting, Milly says that “this entire family is built on secrets [...]. It’s the Story legacy” (61). She then asks Jonah and Aubrey to reveal their secrets, and although they both deny having any secrets to share, the truth of Jonah’s masquerade and Aubrey’s hidden guilt around her father’s affair eventually rise to the surface. When their secrets come out, the teenagers begin to open up and trust one another, and they begin to grow and mature as they learn valuable lessons about honesty and letting go of the past.

Abraham’s famous phrase, “Family first, always” (94), drives Allison to keep the secret of her pregnancy from her mother. Allison believes that covering up shameful behavior is the only way to protect the Story name, and she uses this same notion to justify covering up the truth of what her brothers did to Matt. Secrecy, in this scenario, didn’t just drive a wedge between Allison and the people she loved: it also endangered innocent lives and caused a ripple effect of revenge and fraud that lasted more than two decades.