The Sertori Family is Cleo's family. They are not very close but do love each other. In the starting in the second season Don and Bev divorced with the girls broken up over it. In the third season Don gets remarried to Sam.
Donald Sertori is the father of the family, he was married to Bev and had Cleo and Kim. He and Bev then divorced and Don later married Sam, who he met on Valentine's Day. Don is very protective of his daughters and dislikes most boys. He starts to accept Lewis later in the series.
Cleo Sertori is the oldest child to Don and Bev and the older sister to Kim. Cleo has a secret that none of her family knows about, she and her best friends are mermaids. Cleo looks out for her younger sister and helps her dad out in sticky situations.
Angela is Cleo and Kim's cousin who comes to visit them and tries to go body-boarding. Angela thinks she can get anything she wants and sometimes works with Kim to annoy Cleo. It is not known if she is Cleo and Kim's paternal or maternal cousin.