I’m raising my grandchild and claim her as a tax dependent. If I apply for marketplace subsidies, will we be considered one household?

Yes, for marketplace coverage and subsidies, a household includes the tax filer and the tax filer’s spouse and any tax dependents. Your grandchild may be eligible for Medicaid or CHIP; if she is she will not eligible for premium tax credits for marketplace coverage. However, even if she qualifies for Medicaid or CHIP, you should still include her in your marketplace application as part of your household. (Center on Budget and Policy Priorities, The Health Care Assister's Guide to Tax Rules).