Shizuka Joestar

Shizuka Joestar is a baby found by Joseph Joestar in Part IV: Diamond is Unbreakable.

Story
For unexplained reasons Shizuka has the stand power Achtung Baby, which can turn herself and her close surroundings invisible, including the ground. Despite her prevolent use of her stand power, it is unknown if, and highly unlikely that she is aware of her ability. Upon discovering her Joseph and Josuke are thrown into a wild chase to find her, during which Joseph proves his worthiness to Josuke. From then own Josuke sees his father as more than just any "old man" and instead recognizes him as someone willing to place himself in danger for the sake of protecting an innocent life. Shizuka remains mostly carried by Joseph for the rest the series, who had adopted her into his family despite risking his wife Suzie suspecting her to be another illegimite child of his. Shizuka is made visible thanks to being covered by clothing, heavy makeup and dark glasses. Still, should she find herself very frightened and distressed, the power of her stand will increase making her completely invisible even then.

Trivia

 * Her existence was either forgotten or ignored by Araki, it could also be possible that her stand had no particular use for battle and the Joestars preferred her to stay at their house and live a calm happy life there.
 * Shizuka is one of the only three infant Stand-users, joined by Mannish Boy and The Green Baby.