I thought that Finn in The Force Awakens said that stormtroopers were taken into the academy at an age they don't know their parents and didn't even know their name? So how could those kids in Rebels know their parents and names?
You are confusing stormtroopers of the First Order with stormtroopers of the Galactic Empire.
Star Wars Rebels is set five years before the events of the original trilogy, so these stormtroopers serve the Galactic Empire (the one ruled by Emperor Palpatine). The Galactic Empire phased out clones from the Stormtrooper Corps at the end of the Clone Wars and used volunteers. Since these stormtroopers are volunteers, they joined as adults and obviously know their parents and have a name.