How is Sid's character different from Toms as both Tom and Sid stole some sugar, but Sid let Tom take the blame both times?

In The Adventures of Tom Sawyer, Mark Twain describes both of his characters differently. Sid is the son of the woman whom he is staying with. Aunt Polly is the aunt of Tom, and she is very strict. Sid is described as a very proper boy who never gets into trouble and wears beautiful clothing.

Tom, on the other hand, is a mischievous boy who gets into several troublesome events. Even if Sid does something wrong, Tom always gets blamed for it. He is in love with Becky Thatcher, but Amy Lawrence likes Tom. Both Tom and Sid steal some sugar, but Sid lets Tom take the blame for the incident. Sid doesn’t seem to care and want to take responsibility for his actions like Tom.