This is Greg and his Father. Lets talk about Greg first, Greg is the main character and is also the Round/ Protagonist character. You see Greg in the whole story and he is the Main Character in the story. Now his dad is a Antagonist Character and he is also a Flat Character because you don't see him in the whole story/ he is not talked about in the whole story , and he doesn't change in the story. And just because he is a Antagonist character doesn't mean he is a bad guy.
This is Lemon Brown, and he lives in an Abandoned Old Tenement. He is a Major Character because he is mentioned in the whole story and he is in the story at all times. And he is the Protagonist Character because he protects Greg, The treasure, And himself he also gives Greg Ridley advice about his father.
These are the thugs and they are not so important in the story but we can talk about them anyway. The thugs they don't have names in the story and they are Antagonist characters in the story because they are the bad guys in the story, they are also Minor characters, because they don't change a lot in the story. And they Tried to take Lemon brown's treasure.