Looking for story where time is accelerated on a planet. The characters are actually born at the beginning of the story and then grow up quickly and inadvertently learn that their forebears came from a rocket ship nearby. After having aged to "teenagers" they try to reach the ship? At some point there is a war between confused aging survivors.
Its killing me that I can't find it.
I think it was in a compilation which included a story called "Cousins".