Franklin Richards is the son of Reed and Susan Richards, from the Marvel Universe team, the Fantastic Four. He makes crossover appearances in two different superhero stories in Daria fanfic. Valeria Richards is his sister.
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Daria Von Doom Series
An adult Franklin appears in the Daria Von Doom Series by Richard Lobinske. Younger than Queen Daria, he had a crush on her for several years before going to Castle Doom to assist her in tracking an anomalous teleport signal, that finally was determined to be a time machine used by Kang the Conquerer. During that time, they became romantically involved and by the third story of the series, Succession Crisis, were married and had a daughter, Jane Valeria.
"Outcasts from Beyond"
Franklin Richards also appears in TAG's "Outcasts from Beyond." It is discovered during the course of the story that Ted DeWitt-Clinton is actually Franklin, who engineered a mass rescue of super-powered children from both the Marvel Universe (an alternate universe version in which the first Secret Wars ended in disaster) and the DC Comics universe (another AU destroyed by the Crisis on Infinite Earths). The current universe in which Lawndale resides is a ramshackle construct, a "lifeboat universe" built to save the children and give them a new life. Franklin, however, is no longer sane, and has committed evil acts for the sake of protecting his charges.