Why do you think the author waits until end to reveal that enemy is snipers brother?

The author likely waits until the end to reveal that the enemy is the sniper's brother for dramatic effect. The reader expects some connection between the sniper and the enemy as they are engaged in a life-or-death struggle, but by not making it obvious that they are related and by withholding the twist until the climax of the story, the author is able to heighten the suspense and impact of the revelation.

This unexpected turn of events adds additional depth and emotional complexity to the conflict, giving the reader a new perspective on the situation and providing a compelling conclusion to the narrative.