Everything for the Recovery Rebate Credit will be reconciled on the 2020 tax returns. The payments in rounds one and/or two were advances on the credit on the 2020 tax return.
On the tax return you will get everything you are eligible for which is then reduced by any advanced stimulus payments already received.
So on the father's return he will be eligible for himself and two children claimed. His total eligible amount will be reduced by how much he already received (his stimulus payments).
On your return you will be eligible for yourself and that is reduced by any payments you received already.
Here is a link for more information on the Recovery Rebate Credit.
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