Catherine "Cat" Merriman: The protagonist of the story, a 12-year-old girl who is struggling to adapt to life after her mother's death. Cat is fiercely independent and has a strong sense of justice, but she also carries a lot of pain and guilt.
David "The Dudes" Merriman: Cat's older brother, who is also dealing with the loss of their mother. David is a typical teenager who is trying to figure out who he is, but he loves his sister and tries to be there for her.
Penny Merriman: Cat and David's grandmother, who is also grieving the loss of her daughter. Penny is a strong and caring woman, but she is struggling to cope with her own grief and the challenges of raising two children.
Marty: Cat's best friend, who is supportive and understanding. Marty is a kind and sensitive girl who helps Cat navigate the ups and downs of her life.
Mr. and Mrs. McCreedy: The family that Cat and David live with after their mother's death. They are kind and supportive, but they are also strict and have their own set of rules that Cat struggles to understand.
Other characters:
* Mrs. Merriman: Cat and David's mother, who died in a car accident. Her presence is felt throughout the story, even though she is not physically present.
* Mr. Merriman: Cat and David's father, who left the family when they were young. He is a shadowy figure in their lives and is not a significant character in the story.
* The other children at school: Cat interacts with several other students, but they are not named and their roles are not particularly important to the story.
It's important to note that while the story focuses on these characters, they all have their own stories and struggles, which makes *Rules* a compelling and moving read.