Did Megan Fox play someone's sister?

Yes, Megan Fox played the character April O'Neil in the "Teenage Mutant Ninja Turtles" films, where she is depicted as a close friend and ally of the turtles. However, she did not specifically play a character that is someone’s sister in those films. In other roles, her characters may have familial connections, but her most notable roles do not prominently feature her as a sister.