Editing Personal exemption (section)

===Qualifying children as dependents===
Qualifying children must first be "children" in the sense of § 152(f)(1). The term "children" includes adopted children, children placed for adoption, stepchildren, and foster children. Id. Qualifying children must have the same principal place of abode as the taxpayer for more than one-half of the year and must not have provided more than one-half of their own support. 
§ 152(c)(1). They can include a taxpayer's children, a taxpayer's siblings, half-siblings, or step siblings, or the descendants of a taxpayer's children, siblings, half-siblings, or step siblings. §§ 152(c)(2), (f)(4). They may not have reached the age of 19 by the close of the year, unless they are students, in which case they must not have reached the age of 24, or unless they are permanently and totally disabled. § 152(c)(3).

A child cannot qualify as a dependent on more than one tax return, so the code has a set of rules to prevent this from happening. § 152(c)(4). The code first attempts to break the tie by limiting eligible taxpayers to the child's parents, followed by the contending non-parental taxpayer with the highest adjusted gross income. ''Id.'' If more than one parent attempts to claim the child and they do not file a joint return, the code first attempts to break the tie in favor of the parent with whom the child resided longest during the taxable year. ''Id.'' If that does not break the tie, the parent with the highest adjusted gross income wins the right to claim the child as a dependent. ''Id.''

For the treatment of children of divorced parents, see § 152(e). For a case in which children are missing and presumed kidnapped, see § 152(f)(6)...