Yes, the stimulus payment is calculated based on the number of dependents under 17 plus the taxpayer/s. Your son needs to file 2020 income tax return to receive the stimulus payment. If you received overpayment,none of the stimulus checks are taxable and won't impact your income tax filed this year.
Under the American Rescue Plan Act of 2021 signed in 3/11/2021, a family with household income of $150,000 or less will receive a stimulus of $1,400 per taxpayer and dependents including qualified dependents over 17 years old.
