The Last Kids (2019)

In this post Apocalyptic World, where all of the adults are Zombies (called Hunters) and only kids are Survivors. The Hunters can't climb stairs, so Taven and his cousin Stanley live in a tree house where they have been safe since the Apocalypse started. While looking for food, they rescue a girl and her brother from a group of Hunters, but in the midst of fighting the Hunters, they are helped by a Warrior Girl, named Gianna. Gianna takes the boys to her base camp where travel to meet up with more kids to fight off the Hunters.