I read two books when younger and I keep thinking about them. But have no idea what they are called.
One is about a dystopian world where adults died I think and children were just running riot basically. Think they were in a city, and the main characters were a sister and a brother.
There was another dystopian one that was about two boys who met at a fence between their worlds. I'm pretty sure this isn't boy in the striped pyjamas but might be wrong. One boy was more modern and the other more old fashioned. I'm pretty sure the modern one went over the fence and rose the horses the other boy has but I have no idea.
Any ideas? Not the best descriptions I know sorry. 