What are the four characters in The Act of Squatting by Robert Louis Stevenson?

There are actually only two main characters in Robert Louis Stevenson's "The Act of Squatting":

1. The narrator: He is the main character and a young boy who observes and describes the act of squatting.

2. His father: The father is described as a gentleman and the object of the narrator's fascination and observation.

The story doesn't explicitly mention any other characters, but it does focus on the interaction between the narrator and his father.