Sofia the First is the main protagonist of Sofia the First: Once Upon a Princess. She is a cute and beautiful young girl who unexpectedly becomes a princess when her mother Queen Miranda marries the king, Roland II. She has trouble as a princess, ranging from getting bullied by her step-sister Princess Amber, being clumsy, and a sorcerer named Cedric who wants to rule the kingdom. But, with help from her friends, she can handle these problems.
When Sofia became princess, she was excited that she would be sisters with the other princess Amber. Unfortunately, Amber was rude and spoiled, and she didn't want to be sisters, occasionally correcting Sofia by stating that they were only step-sisters. Amber was jealous because Sofia was getting more attention than her. Amber played pranks on Sofia and even tricked James into doing the same. Sofia was initially unaware of this, but soon found out after Amber gave her magic shoes. After Amber humiliated her, Sofia refused to talk to her. Amber didn't care though, but after she was scolded by James and had her dress ripped, Amber became depressed and didn't come to the royal ball. Soon after, Amber realized her mistakes and helped Sofia, even protecting her from Cedirc's raven Wormwood. Amber then taught Sofia to dance.
Sofia thought that she and James would be good friends, but she didn't seem to be as excited to have him as a brother as she did Amber as a sister. Ironically, Prince James was kinder to her than Amber. They had a rough start though, because Amber tricked James into embarassing Sofia, and she thought James did it on purpose. James made it up to her by helping her occasionally, and brought her to dancing lessons, but Amber used this as another opportunity to prank Sofia. James tried to stop Amber from bullying Sofia by berating her, which depressed Amber. After Amber made up with Sofia, James has helped Sofia with her problems, including helping her ride the horse Minimus.
Miranda is Sofia's mother, and they care for each other.