Jem (Jeremy Finch)
Jem Finch is the son of Atticus and the older brother of Scout. He is always looking to try to impress his dad and throughout the story he significantly grows more mature. He always seems to be doing something he's not supposed to be, such as going around the Radley house. Jem is always looking after Scout and also acts like an older brother to Dill by looking after him and also when he told on Dill for running away from home so he wouldn't get into anymore trouble.
The event that changes Jem is the moment when he turns Dill in for running away from home. Jem turned Dill into Atticus because he didn't want Dill to get in anymore trouble than he already was in, and he wanted to show Atticus that he was growing up. This is a big event in the story for Jem because it marks the point when he starts to strive to reach adulthood.