<P> The Bobbsey Twins are the principal characters of what was, for many years, the Stratemeyer Syndicate's longest - running series of American children's novels, penned under the pseudonym Laura Lee Hope . The first of 72 books was published in 1904, the last in 1979, with a separate series of 30 books published from 1987 through 1992 . The books related the adventures of the children of the upper - middle - class Bobbsey family, which included two sets of fraternal twins: Nan and Bert, who were 12 years old, and Flossie and Freddie, who were six . </P> <P> Edward Stratemeyer himself is believed to have written the first volume in its original form in 1904 . When the original series was brought to its conclusion in 1979, it had reached a total of 72 volumes . At least two attempts to restart the series were launched after this, but neither effort saw the popularity that the original series achieved . </P>

What are the names of the bobbsey twins