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Do you have your two adult pairs housed in the same cage? If so, and in order to avoid complications, it's best to separate the extra pair into a different cage and let the breeding couple in the cage to continue to tend to the chicks.
Since the chicks will very soon be at weaning age, you should pay close attention to the mother and to see if the chicks aren't being neglected nor being victims of aggression on the mother's part. At about 3.5 - 4 weeks old the mother will start to spend more time out of the nest and this will encourage more matings between the breeding pair and if not stopped, this will lead to a second clutch and as the mother tries to tidy the nest, she will start to neglect her chicks and force them to get out of the nest. During these attempts the chicks can suffer abuse and be attacked.
This is why it's recommended to separate the mother once the chicks reach weaning age, not only will it prevent a second clutch from happening and giving the mother a much deserved rest, but this measure will also prevent the chicks from being attacked. During this time, the father will take a more active role in feeding the chicks and help them with the weaning process.
We as owners/breeders can also do our part in helping the chicks during this adjustment period where they start to learn how to eat and be self-sufficient.
In terms of taming, you could have started handling the chicks sooner in order to make them used to you. Daily nest checks are needed in order to see if the chicks are being well fed and are developing well in terms of growth, not to mention the regular cleaning of the nest.
You can start to gently pick the chicks up and talk to them in a positive and encouraging way. You can start with short sessions of 5 - 10 minutes, but you must be aware to not interfere with the parents feeding schedules. It's best to handle the chicks after they have been fed.
Setting up a play area will also be of benefit for the chicks and you can also have a little feeding station to help them out in trying all the "grown up" foods.
Please be sure to read this link below for all the detailed information.
It will also be good if you would take your time in reading the sticky threads at the Budgie Breeding as well as the Taming and Bonding section.
I have also moved your thread to the Budgie Breeding section, where it's most appropriate.