Pick each baby up at least once a day to hand tame them. Scritch the baby the same way you would as the parent birds, even if they don't have all their feather yet. Start them with step up training when you are holding them and keep up the training as they age and get older. When they fledge (start perching on their own and leaving the nest), they will have a reaction to you trying to pick them up, be firm about picking them up, but try not to chase them around to pick them up. I usually trap the babies in a corner of the cage with a piece of cardboard, then pick them up. You don't have to hand feed to hand tame and acclimate the babies to humans.