Joy, Aranea and Nellie were three of Charlotte's 514 children. They are mentioned at the end of the book. In "Miracles do happen", a second "Charlotte's web" novel, Nellie has been separated from her sisters Aranea and Joy and becomes the new Charlotte for Wilbur, writing various words in her webs from various visions given from Charlotte's spirit and Virgil.
They are seen at the end of the film. In "Miracles do happen", Nellie has been separated from her sisters Joy and Aranea and must follow Charlotte's ghost to find Easter's Eye and deliver it to her sisters and Fern Arable. She also has a boyfriend, Fico the male hobo spider, and at the end of the film, thanks to Wilbur's selfless sacrifice, Nellie and Fico are blessed by Easter's Eye to outlive Charlotte 15 times to see and raise their children as true parents.