In the popular Chinese classic Romance of the Three Kingdoms, one of the main characters, Liu Bei, actually has 2 sidekicks, his sworn brothers Guan Yu and Zhang Fei. They were introduced quite early in the story and, from then on, were always together. So there could be more than one sidekick for the main character. In the same vein, you could say that Harry Potter's 2 sidekicks are Hermione and Ron Weasley. However, I think 2 sidekicks is the maximum possible. Any number more than 2 is bound to run into problems of multiple interactions between the characters and dilutes the impact of the main character. When you have more than 3 characters, you have an adventuring party!