Jojo Siwa is the youngest of these celebrities with a birthdate of May 19, 2003. Millie Bobby Brown was born on February 19, 2004, and Willow Smith was born on October 31, 2000. Therefore, Jojo Siwa is the youngest among them. She is an American singer, dancer, actress, and YouTube personality. She gained popularity on the reality TV show "Dance Moms" and has since made a name for herself as a pop star with hit songs like "Boomerang" and "D.R.E.A.M." Siwa is also known for her distinctive style, which includes wearing bows in her hair and bright, colorful clothing.