No, the IRS will not take your refund to pay your Stepson's IRS debt if you claim him as a Dependent.
You may be able to claim your Stepson as a Dependent, if ALL of the following requirements are met:
- He is a citizen of the US
- He has taxable income of less than $4,150 during 2018
- He is not a qualifying Dependent of someone else
- He is not filing a joint return
- He lived with you all year if he is not under age 19 or under age 24 and a full time student.
- You provided more than 1/2 of his support.
You can also check out this IRS Tool which walks you through a set of questions to help determine if you can claim someone as a Dependent: https://www.irs.gov/help/ita/whom-may-i-claim-as-a-dependent.
