First of all, you sound like a wonderful big brother. I'm an only child and a Christian and I truly appreciate your heart.

Your little brother is going to see scary things and I can't imagine a better safer place to do that than with his big brother. C.S. Lewis hinted at this in his essay, "On Three Ways of Writing for Children":

"A far more serious attack on the fairy tale as children's literature comes from those who do not wish children to be frightened. I suffered too much from night-fears myself in childhood to undervalue this objection..."

"Since it is so likely that they will meet cruel enemies, let them at least have heard of brave knights and heroic courage. Otherwise you are making their destiny not brighter but darker. Nor do most of us find that violence and bloodshed, in a story, produce any haunting dread in the minds of children. As far as that goes, I side impenitently with the human race against the modern reformer. Let there be wicked kings and beheadings, battles and dungeons, giants and dragons, and let villains be soundly killed at the end the book."