Shizuka Joestar

Shizuka Joestar is the a baby found by Joseph Joestar in part 4.

Story
For unexplained reasons Shizuka has the stand power "Actung Baby", named after the U2 album. Which can turn anything invisible. Upon discovering her Joseph and Josuke are thrown into a wild chase to find her and which Joseph proves his worthiness to Josuke. From their own Josuke sees his father for more than just and "old man" instead seen him as someone willing to place themselves in danger to the sake of protecting an innocent life. Shizuka reminds in Joseph's hand for most of the series. She is see-able because Joseph dressed her up and gave her glasses. When shopping for baby things, Joseph ends up paying much too much money for baby supplies.

Shizuka's stand power is to turn herself and everything around her invisible, depending on her mood. It works in many ways, making her unfindable underwater to Joseph, or making 2 of Rohan's fingers invisible.

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 Joestar preferred her to stay at their house and live a calm happy life there.