Joestar Group

"The youth of this town have a golden spirit. The same golden spirit shining with justice we saw on our journey to Egypt. That spirit they embody will naturally course into others without a word..."

- Joseph Joestar,

The Joestar Group is a nickname given to the team of protagonists prominent in each part of JoJo's Bizarre Adventure. The group is composed of different members in each part, but generally consists of a JoJo and various other allies all following the same or a similar plan of action (i.e defeating DIO or protecting Morioh).

History
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Phantom Blood
The original Joestar Group starts in the year 1889 with Jonathan Joestar, aided by his allies Will A. Zeppeli and Robert E. O. Speedwagon. Although Bruford was originally an enemy, he respects Jonathan after their battle and gives him his sword, Luck and Pluck. Later on, Dire, Straizo, Tonpetty and Poco assist Jonathan in an effort to deter the incoming threat to mankind, Dio Brando.

Battle Tendency
50 years later, in 1939, Jonathan's grandson Joseph, along with his partner Caesar Zeppeli, their mentor Lisa Lisa, and Nazi major Rudol von Stroheim, engage the creators of the Stone Mask, the Pillar Men.

Stardust Crusaders
49 years later, in 1988, Jotaro Kujo, the grandson of Joseph Joestar, learns that DIO has returned from the bottom of the ocean. Jotaro, who has now acquired a Stand called Star Platinum, journeys to Egypt to defeat DIO and release his mother Holy from DIO's curse, with help from his grandfather Joseph, Muhammad Avdol, Noriaki Kakyoin, Jean Pierre Polnareff and a dog named Iggy.

Diamond is Unbreakable
11 years later, in the year 1999, the illegitimate son of Joseph Joestar, Josuke Higashikata with his Crazy Diamond takes it upon himself to protect Morioh from enemy Stand users after his grandfather is killed. He is aided by Jotaro, his classmates, and a strange mangaka. They target Stand users who use their Stands to harm others such as Angelo, Akira Otoishi, and Yoshikage Kira.

Vento Aureo
2 years later, in 2001, Giorno Giovanna, the son of DIO, joins Bruno Bucciarati's team of Passione gang members in order to rise within the ranks and overthrow their mysterious boss, who is flooding the streets of Italy with drugs. By doing so, Giorno hopes to set the mafia's moral standards straight again. The group is also aided by Polnareff and Koichi who are members of previous Joestar Groups.

Stone Ocean
Ten years later, in 2011, Jotaro's estranged daughter, Jolyne Cujoh, is incarcerated for a crime she didn't commit and is in a deadlock against the remnants of DIO, led by his most devout supporter, Enrico Pucci. Her goal is to save her father, escape prison, and survive. She is helped by her father, Emporio Alniño, Ermes Costello, Foo Fighters, Weather Report, and Anasui.

Steel Ball Run
In an alternate universe, in the year 1890, Johnny Joestar along with Gyro Zeppeli rides coast to coast to compete in the Steel Ball Run. They discover the Saint Corpse Parts while racing, which gives them Stand powers and greatly improves their physical abilities. The duo is hunted by many people during the race, including other racers, mercenaries, & even the president.

JoJolion
120 years later in 2011, Josuke Higashikata is joined by his love interest Yasuho Hirose, friends from his past and adoptive family, as they work together to discover Josuke's original identity. Their investigations lead them to uncover the Higashikata Family's deepest secret and run afoul of the mysterious Rock Humans.

Non-Canon Members
In JoJo's Bizarre Adventure: Eyes of Heaven, Jotaro Kujo and Joseph Joestar join forces with the remaining main JoJos of all 8 parts of the series, as they work together to collect all the Saint's Corpse parts and defeat Heaven Ascension DIO.

The main JoJos are assisted by a large group of allies, lead by Robert E. O. Speedwagon. Some of the allies had originally died and been possessed by DIO, but were freed from DIO's control and revived via the Saint's Corpse.

Similarities

 * The majority of the Joestar Groups are not led by the main JoJo, but rather by an ally:
 * Phantom Blood's Joestar Group was initially led by Will Anthonio Zeppeli before his death, all the while he was teaching Jonathan Joestar the basic mechanics of the Ripple.
 * Battle Tendency's Joestar Group was led by Lisa Lisa, the Ripple Instructor of Joseph Joestar and Caesar Anthonio Zeppeli, as well as the strategic leader in the war against the Pillar Men.
 * Stardust Crusaders' Joestar Group was led by Joseph, the eldest of the Crusaders, who initiates the mission to find DIO and fight him in Egypt.
 * Diamond is Unbreakeable's Joestar Group was led by Jotaro Kujo, the main rallying force for the active hunt for throughout the part.
 * Vento Aureo's Joestar Group was led by Bruno Bucciarati due to him being the direct superior of every member, in addition to him acting as a father figure to the group in general.
 * Stone Ocean's Joestar Group is the first group to be led by the main JoJo, Jolyne Cujoh. She leads the group's actions and commands the respect of her companions.
 * Steel Ball Run's Joestar Group is a partnership, with Johnny Joestar and Gyro Zeppeli agreeing to work together to reach each other's goals. However, Gyro possesses a tacit leadership role due to him teaching Johnny the Spin.
 * JoJolion's Joestar Group is the second group led by the main JoJo of the part, as Josuke's will to uncover his identity is the main drive behind the duo's actions and later he joins up with Rai Mamezuku in order to retrieve the New Locacaca branch.
 * Eyes of Heaven's Joestar Group is lead by Jotaro and Joseph, and their group of allies is lead by Speedwagon.
 * With the exception of Battle Tendency and Diamond is Unbreakable, most of the members in any Joestar Group die (or at the very least never seen again) before the end of their respective parts with very few carrying over to the next respective part. (i.e. Speedwagon, Joseph, Polnareff, Jotaro, and Koichi).
 * Diamond is Unbreakable and Jojolion share many similarities, mostly due to the latter being somewhat of an alternate-universe adaptation of the former:
 * Both main JoJos of the group are illegitimate children, and share the name Josuke Higashikata.
 * Both feature members of the Hirose Family, and each member shares a musical reference in their Stand's names with their respective Josuke - Diamond is Unbreakable 's are both songs, while JoJolion 's are  songs.

Trivia

 * Though not initially planned, Araki threw around the idea of Hol Horse joining the protagonists of Stardust Crusaders during their journey, but opted out due to balance issues with Polnareff's similar character. Araki mentions this is part of the reason Hol Horse shows up multiple times throughout the story and why there is at least one group shot with Hol Horse present.
 * Dio Brando once dismissively called Jotaro's own group the Joestar Egyptian Tour Group (ジョースター・エジプト・ツアー御一行様).