Who is Carulina from History: A Novel and what is their importance?

Carulina is a fifteen-year-old member of The Thousand family. She was impregnated at fourteen, but does not know who the father is. Carulina gives birth to twin girls, Rosa and Celeste and, although she is not healthy herself, tries to be a good mother to them in spite of the fact that she is still a child, herself.