Yes it is. If you were getting the "stimulus" checks as a recovery rebate credit on a tax return then any part of your tax refund can be seized for child support that you owed. The IRS or the state can seize your income tax refund if you owe child support.
https://turbotax.intuit.com/tax-tips/tax-payments/who-can-garnish-an-income-tax-refund/L7cPPzDyc