Responses
Yeah your so right and MC only just became mature due to the trauma of losing his family before that he was extremely selfish and childish as an adult!
And of course the little sister is going to cling to her big brother she lost her father so young and her brother stepped up to be the man of the house. So course as a child she's not going to react rationally to the though of him leaving her behind.
Yes they are childish but remember they are CHILDREN. They aren’t mature adults only the mc is. They are children with their own issue that they are struggling with give them time to grow and mature.