My wife has custody of her two children from a previous marriage. She gets to claim one child and her ex claims one. He is currently very far behind on child support and the Child Support Enforcement office is garnishing any income tax refunds.

However we have not received any in several years. We believe that his new wife is claiming the child and they are filing separate returns. That way the IRS can't garnish the refund.

Is this legal? Can a non-custodial step parent claim a child on the tax return?

Any info would be greatly appreciated.