After nine years of marriage and two stillborn children, her parents had little hope for healthy children; and so Caroline's birth was a great joy. About three and a half years later, another girl, 
Anna, was born but survived for only six weeks. Fearing the extinction of this branch of the Orange-Nassau family and a possible loss of the "Stadhouderschap", it was decreed in 1747 that the position could be inherited by females as well. However, in 1748 when Caroline was five
years old, a brother, the future Stadhouder Willem V, was born.Caroline was a happy child; musical and artistic, she wrote poetry and played the piano. She was fond and protective of her little brother, and all her life remained close to him, and he always remained willing to listen to his sensible sister.
In 1751 the family's peace was disturbed with the sudden death of their father. Their mother, Anna of Hannover, then became regent for the three-year-old Willem V Batavus. In 1755 her mother began negotiations for Caroline to marry her German cousin, Karl Christian of Nassau-Weilburg, without the knowledge of the Dutch government.
Anna thought this almost penniless prince perfect as he would not object to living in The Netherlands, in case Willem V died leaving his sister heir to the "Stadhouderschap". However, the Dutch government didn't think him good enough for this grand-daughter of King George II
of Great Britain. Anna of Hannover died in 1759 and a year later the 17-year-old Caroline married her German cousin after all. They remained in The Hague to be near her 12-year-old brother. In all,
Caroline and Karl Christian became the parents of fifteen children.
After the birth of a second son, they had to move to Germany to take control of several inheritances, but later returned to The Hague on a regular basis; and there, in 1765, they met the 9-year-old Mozart. She invited him several times and Mozart wrote six sonates for clavecimbel
and violin dedicated to Caroline. When Mozart became ill, she sent him her own doctor.
Caroline and her husband built a palace in The Hague which became an artistic centre. When her grandmother, Regent for Friesland, died in 1765, it was Caroline who became regent for her brother in the northerly provinces. In 1784 Caroline and her family moved for good to Germany, at a time when her lack-lustre brother needed her most. The large number of children had taken its toll on her health and she died in 1787, only 44 years old.
 

Source: Leo van de Pas