The American family is changing. Individuals marry later, divorce more frequently, or live together without being married. Nonmarital births, complex custody arrangements, and multiple generations of families living together are more common, but the tax system has not kept pace. Although tax benefits are an important pillar of support for children, understanding who in a complex family should claim them can be difficult. We document demographic trends and explain their importance with respect to tax filing and eligibility for child-related benefits, such as the earned income tax credit, child tax credit, and dependent exemption.