Somerville was born on December 26, 1780, in Jedburgh, Scotland. She was the fifth of seven children. She was one of three who lived to be adults. Her father, William George Fairfax, was a vice-admiral in the Royal Navy. He would go on long trips away. Somerville's mother didn't try to educate her daughters; she thought that all girls needed to know was how to cook and clean. When Somerville wasn't doing household chores, she would often go to the seaside and the moors.