Star Birthmark

The Star Birthmark (星のアザ) is a distinct, five-pointed, star-shaped mark appearing in the region of the back of the left shoulder or close to the nape on all JoJos or individuals of the Joestar bloodline. It may also appear on individuals who are connected to the bloodline in certain ways.

It was introduced in Stardust Crusaders and becomes important again in Stone Ocean. The anime incorporates the birthmark earlier, depicting Jonathan Joestar and Joseph Joestar with it. It resurfaces in the second continuity within JoJolion.

Original Continuity
The origin of the star-shaped birthmark is unknown, but within Phantom Blood onward, every member of the Joestar family by blood bears the birthmark. At the end of Phantom Blood, Dio Brando murders Jonathan Joestar and takes over his body. Through this process, he inherits the birthmark but rests at the bottom of a sea for a century. Later, in 1983, DIO reawakens after escaping his coffin. He travels around the world and impregnates multiple women with his children, notably Giorno Giovanna, the protagonist of Vento Aureo.



The birthmark is only formally introduced in Stardust Crusaders by Joseph Joestar to Jotaro Kujo, being how he recognized Jonathan Joestar's body on DIO in the spirit photograph of him. With DIO's reawakening, the special connection he gained through Jonathan's body puts Holy Kujo in danger, so they set out to destroy him. A few years before these events, Joseph Joestar has an affair that results in Josuke Higashikata; who as a part of the Joestar family, inherits the birthmark.

In Stone Ocean, the birthmark becomes integral once again. Jotaro Kujo's daughter, Jolyne Cujoh, faces off against an eccentric priest, Enrico Pucci. During the events of Stone Ocean, Pucci fuses with the Green Baby and gains the birthmark, as the creature originated from DIO's Bone. His brother, Weather Report, also receives the mark; as twin brothers, they connect and affect one another in the same way DIO does with Joseph, Holy and Jotaro in Stardust Crusaders.

At the end of the story, Emporio Alnino enters the new universe where he discovers Irene, a woman nearly identical to Jolyne, who shockingly possesses the mark.

Characters of the original continuity's Joestar family who were not depicted with the birthmark include George Joestar I, George Joestar II, and Donatello Versus.

Second Continuity
Like the original continuity, the origin of the birthmark is unknown but seemingly all members of the Joestar family by blood bear it. Johnny Joestar's is never shown but Lucy Steel is aware of it. His grandson, Joseph Joestar, bears the birthmark, and his Stand protrudes out of it.

Later on, in JoJolion, the protagonist Josuke Higashikata bears the birthmark through seemingly unknown means. It is eventually revealed that he inherited this birthmark through a Locacaca fusion of Yoshikage Kira. Kira's sister, Kei Nijimura, also bears the birthmark. The Star Birthmark plays into Josuke's usage of his bubbles and the Spin, as the bubble comes out through it.

In The JOJOLands, Dragona Joestar is shown to inherit the birthmark from their grandfather Joseph Joestar, while Jodio and Barbara Ann Joestar are yet to be shown bearing it.

As well as Johnny Joestar, characters of the new continuity's Joestar family who were not depicted with the birthmark include George Joestar II, Nicholas Joestar, George Joestar III, and Holy Joestar-Kira.

Trivia

 * Both Jonathan and young Joseph weren't depicted with the Star Birthmark in their respective parts due to the concept not being introduced until Stardust Crusaders. Jonathan's was later included in the Phantom Blood film, 2000 Stardust Crusaders OVA, and the anime adaptation. Young Joseph's birthmark was included in the anime adaptation as well.
 * Josuke also wasn't depicted with the birthmark in Diamond is Unbreakable until the anime adaptation of the part.
 * An artwork in the Hirohiko Araki JoJo Exhibition 2012 shows Lisa Lisa with the birthmark, despite being from a different family and not being biologically related to the Joestar Family.