Originally, Final Fantasy II and III for the Famicom and V for the Super Famicom were not released in America. For number continuity, Square of America changed the numerals of the US releases: Final Fantasy IV became "II" and VI became "III". Starting with Final Fantasy VII the pretense was dropped, and all subsequent games used their original numbering, leading to an apparent "jump" over 3 games. This has been a source of much confusion, with many American fans continuing to refer to IV and VI by their American numbers. To solve this, many fans use the disambiguative suffixes "us" and "j" for American numbering and Japanese numbering respectively, e.g. FF3us or FF6j. Later ports include translations of the Japanese games with their original numbering.
Until the release of Final Fantasy X-2 the idea of a "direct sequel," that is, a game which picked up directly from the story of a previous game in the series, was unprecedented in the series. Starting with that game, however, several such sequels emerged, especially the Compilation of Final Fantasy VII series of games/movies, all of which continue the story of the game Final Fantasy VII. This is most likely a result of the merger with Enix, which was well-known for producing sequels and spinoffs associated with the Dragon Quest series.
Released in North America as Final Fantasy Legend III
These games are technically part of the SaGa series, but used the Final Fantasy brand for their English language releases. Subsequent games in the series were released under the SaGa brand.