Should they keep my refund if I pay child monthly out of my paycheck?

[xmasbaby0]

If you are current  -- up to date --  in your child support payments then your tax refund should not be offset.  But if you owe delinquent child support from the past, even if you are making payments now, your refund can be offset for the back child support owed.  TurboTax never knows about child support or back taxes you owe.  

Reduced Refund      https://www.irs.gov/taxtopics/tc203

 NOTE: You can contact the IRS Treasury Offset Program Call Center at 1-800-304-3107 to ask if they have an offset for you on file. TurboTax would not have that information.

https://turbotax.intuit.com/tax-tips/tax-payments/who-can-garnish-an-income-tax-refund/L7cPPzDyc