Queen Lucy the Valiant“She is never first–not until Narnia. She is the youngest and the smallest, the one the others must protect from the reality of their shattered, collapsing world. But then she crawls through a wardrobe into a land of magic and.
It's a toss up between this one and Peter/Edmund brotherly relationship or Susan/Lucy sisterly relationship or Peter/Lucy sibling relationship. Sorry Susan/Edmund sibling relationship, it didn't do it for me.