A main worry of the eldest Curtis brother is being able to keep custody of his two younger brothers, but this plot line is hardly mentioned in the movie.
The introduction of Ponyboy in the book and in the movie are completely different and there's not a clear reason why it was changed for the movie as it's arguably a weaker introduction in the movie than it is in the book.
The book makes it clear that Ponyboy is writing his story for a school project while the movie never fully specifies why Ponyboy is telling the audience his story. The book emphasizes the fact that Ponyboy's a great writer and student, but the movie never delves into this character development.
