Nothing prevents a Taxpayer from filing a tax return even if claiming a dependent would not result in a refund, but why they would do so, you would have to ask them (and know that they has no taxable income).
If you are not the custodial parent for tax purposes, where the child lived at least 183 nights or more in 2017, then you would need a 8332 form from the other parent whether that parent files a tax return or not.
If the child did live with you more than 183 nights then you don't need the 8332 form. Either way, it makes no difference to you whether the other parent files a tax return or not - the requirements are the same either way.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
