What does birthmark represent?

Sylvie’s birthmark symbolizes the inevitability of truth. Ma, Pa, Willem, and Helena decided to keep Sylvie’s true parentage secret, but Sylvie eventually discovers the truth when she realizes that she and Willem have identical birthmarks. The truth emotionally destroys Sylvie, in part because it was kept from her for so long., and thus the novel reemphasizes the destructive nature of secrets.