There are various origin stories for the Fantastic Four, but this is the basic one. The Fantastic Four was a team of scientists and astronauts who were doing an experiment in Space. An accident on return to Earth happened. The ship traveled through a cosmic storm and exposed the team to the storm’s rays of energy, with each crew member given fantastic super powers and abilities.
In "Ultron-5", Red Ghost with his Super-Apes manages to infiltrates to the home of the Fantastic Four. But arriving he found Black Panther and Hulk, who easily defeat him and his Super-Apes.
In "The Private War of Doctor Doom", The Thing and the Human Torch went to the Avengers Mansion to play cards. Meanwhile, Janet and Tony went to visit Sue and Reed. Doom uses these meetings to attack them simultaneously. Reed did not understand why Doom attack them knowing that they were accompanied by the Avengers. After a fierce battle, Doom decided to release Janet and Sue. It is revealed at the end that the Invisible Woman was replaced by a Skrull.
When the Skrull invasion began, the Invisible Woman (Skrull) sent the Baxter Building to another dimension but the Real Invisible Woman could enter that dimension and return it to its place of origin.
While the whole team does not appear in the film, but gets mentioned, instead, the Earth-838 version of Reed Richards/ Mr. Fantastic appears in the film, with John Krasinski providing the character's portrayal. Invisible Woman also gets referenced in the film.
While the whole team does not appear in the film, Johnny Storm/Human Torch from an unspecified universe appears in the film, with Chris Evans reprising his role from the 2005 film. He is alive in The Void, but it is unknown what happened to the rest of his teammates from his world.
However, before 21st Century Fox aquired the film rights in 2002, they were held by Bernd Eichinger of Constantin Film during the 1990s. To maintain the rights, Eichinger produced a low-budget Fantastic Four film that was never intended for a theatrical release.
Benjamin Grimm/Thing is the only member of the team who is not related to the other heroes.
The Fantastic Four is Marvel Comics first superhero team, setting a precedent for the formation of other teams like the X-Men and the Avengers. They are one of the most recognizable and influential comic book groups.