Your household size is the number of people you claim as exemptions on your federal tax return who live in your home. In your household size, you can include your child of whom you have primary custody, even if you allowed the child's other parent to claim the exemption on his or her tax return. You cannot include people you are entitled to claim on your tax return who did not live with you in your home during 2012 or who aren't related to you. For the purposes of this credit, an individual cannot be counted in household size on more than one return.