The Bobbsey Twins are the principal characters of what was, for many years, the longest-running series of children's novels. The books related the adventures of the children of the middle-class Bobbsey family, which included two sets of fraternal twins: Bert and Nan, who were 12 years old, and Flossie and Freddie, who were six. Share the stories of your childhood with your children and grandchildren! Here are the original Bobbsey Twins adventures.