I love how different the relationships that Noah and Charlie have with their respective younger brothers.
Charlie and Otis have the typical sibling relationship of annoying each other, with Charlie having a sign that has Otis' name with a cross on her door. Charlie wouldn't have mind to take Otis to his karate lessons if her bike wasn't her only ride at the time. She also refuses to help feed the family dog, Conan, saying he's Otis' pet.
However, they do show that they love each other. Charlie does ruffle Otis' heir affectionately at one point in the movie. When Otis learned about Bumblebee, he instantly wanted to come along and help his sister. Charlie, of course, refuses and tells him to stay home since it's dangerous and trust him to keep their mother and stepfather from noticing she's gone. They even hug right after Otis wishes Charlie good luck on her rescue mission.
Even after failing to keep their mother from finding out that she was gone, Charlie knew that Otis did his best, saying their family helped her and Bumblebee save the Earth.
Noah and Kris are obviously close. Noah shows to cook for Kris, making sure that he tells him when he is in pain, and takes Kris to his doctor appointment despite their mother asking if Noah is certain to do it since Noah already had a job interview on the same day.
After Noah's interview was cancelled, Kris tries to cheer up his brother by comparing him to Superman. After this, Noah decided to join Reek to steal a car in an attempt to pay for Kris' medical bills, despite knowing how risky it would be and how anything could go wrong.
After learning about the Autobots and how their planet is in danger, Kris, much like Otis, wanted to come along and try to help. Only for Noah to tell him that it's dangerous and to look after their mother. However, Kris is aware that his big brother might not come back, something that Noah can't deny. Kris tells Mirage to protect his brother, even saying that he'll come after the Autobot if he does fail his promise.
When Noah feels that he failed to stop Scourge and Unicron from destroying the Earth, he apologizes to his little brother through the walkie-talkies for not protecting their planet. Kris tells Noah that whenever the former wanted to quit because of his sickness, Noah always told him to never give up. Kris even tells Noah that now it's his turn not to give up and that he's the strongest person Kris knows.
I'm not saying which sibling relationship is better than the other one since Charlie and Noah have different circumstances surrounding their home lives that affect their relationships with their brothers and mothers, but I think it's interesting the two movies show different types of older and younger siblings.
