You really can't blame apple for you just being dumb. Apple did the right thing, they signed in with your username and password and apple sync'd to the new dev

You really can't blame apple for you just being dumb. Apple did the right thing, they signed in with your username and password and apple sync'd to the new device. The only missing family feature is multiple accounts on an iPad, but the problem you're having is that you shouldn't have given your children your apple id to set up their devices with... Like everyone else is telling you, setup your children's devices with their own iCloud accounts.