Those tricky tax laws, always getting in the way of tax preparation.

Those silly tax laws - why would they keep these things secret?

You need to review what is considered the Enhanced Child Tax Credit through the new tax law.  It is available to dependents over 17, mothers, fathers, others that you may claim and has specifics about it.

i don't know if this applies for what you're asking but found this via google https://www.forbes.com/sites/kellyphillipserb/2018/08/28/irs-issues-guidance-on-new-500-credit-for-d...  it reads in part, "The Tax Cuts and Jobs Act (TCJA) made a number of changes that affect the tax burden of families. However, those changes did lead to some questions. Today the Internal Revenue Service (IRS) announced that it intends to issue proposed regulations to clarify who is a qualifying relative for the new $500 credit for dependents and head of household filing status."