The Sinclair family matriarch, Tipper passes away just before summer fifteen. More subdued than he used to be, Harris treats Cadence with tenderness. Following the loss of Clairmont, he rebuilds the house in a modern style and doesn't put any possessions in it. His manipulative behavior prompts the Liars to burn his house on the island. Full of ideas about hard work and American traditions, he sets his children against each other and uses his wealth as a tool with which to control them. Harris is the head of the Sinclair family. She also appears to be suffering from an illness that gets worse as the summer goes on. The post-death version of Mirren who interacts with Cadence during summer seventeen boasts of a boyfriend who doesn't exist. She is possibly the least disturbed about the fighting between the Sinclair sisters and was also the grandchild closest to their grandmother, Tipper. The youngest of the Liars, Mirren is Aunt Bess's oldest daughter, and third in the Sinclair grandchild pecking order. Gat's frustration at Cadence's family's racism becomes a factor in his and Cadence's plan to burn down Clairmont. Gat is of Indian descent just as Granddad does not consider his uncle a suitable husband for Carrie because of his ethnicity, Gat is considered an unsuitable boyfriend to Cadence. As Aunt Carrie's boyfriend's nephew, Gat has spent summers on Beechwood Island since childhood. Having been convinced by Gat and Cadence, Johnny takes part in the arson that leads to his death. He is particularly close to Mirren, and tends to assume responsibility for most of the Liars' exploits. Only a few weeks younger than Cadence, Johnny still assumes somewhat of a leadership role within the Liars, especially during Summer Seventeen when Cadence is finally allowed to return to Beechwood. Drunk herself at the time, Cadence accidentally burns the main floor of the house while her fellow arsonists are still in the house.

Cadence eventually pieces together her memory, recalling that she, Mirren, Johnny, and Gat (known to the family as the Liars) decided to burn down their grandfather's house on the island as a protest against the family's drunken fights over their inheritance.

As the novel goes on, it is revealed that Cadence is suffering from post-traumatic stress disorder, which prevents her from remembering exactly what happened. After a traumatic brain injury that happens during summer fifteen on her grandfather's island, she appears to need more guidance and confidence-bolstering from her cousins who she feels are ignoring her, but she doesn't know why. She is in love with Gat, the nephew of her aunt Carrie's partner.

Cadence values her family and treasures the summers they spend together. The narrator and protagonist of the novel, Cadence is the oldest of the Sinclair grandchildren.

We were liars and family of liars