What are the motifs in The Thirteenth Tale by Diane Setterfield?

There are many secrets within this book that motivate many of the characters to action. Aurelius is a living, breathing secret, the child of one of the Angelfield twins but unaware of which is his mother and why she abandoned him. Margaret suffers under the burden of the secret her mother chose to keep from her, the secret of her twin's birth and death. This secret has divided Margaret from her mother her entire childhood and caused their relationship to be non-existent. Isabelle has a secret that she keeps from her entire family: Her husband was not the father of her twins. Her brother Charlie was.