Five was born Karin Cecilie Kullmann in Bærum, the daughter of a dentist, and was better known by the nickname "Kaci" (). After finishing upper secondary school at Nadderud in 1969 she was educated in law, French language and political science, and graduated with the cand.polit. degree in political science at the University of Oslo in 1981. Before she entered politics she was a consultant at the Norwegian Confederation of Norwegian Enterprise (NHO). In 1972 she married Carsten O. Five, former editor of the finance magazine "Dine Penger". They have two children.