The Twins (Dutch: De Tweeling) is a 1993 novel by Tessa de Loo about the sisters Lotte and Anna, who are separated at the age of six when their father dies.
She suffers from osteoarthritis and the treatment she is taking is intended to relieve her pain.
On the third day, she meets a German woman of her age in the restroom of the Thermal Institute.
It soon becomes clear that the German, Anna Grosalie, is Lotte's twin sister.
Due to bad relations within the family, but especially because of the war, the two sisters lost touch with each other.