child
(A)The term “child” means an individual who is— (i)a son, daughter, stepson, or stepdaughter of the taxpayer, or (ii)an eligible foster child of the taxpayer. (B)In determining whether any of the relationships specified in subparagraph (A)(i) or paragraph (4) exists, a legally adopted individual of the taxpayer, or an individual who is lawfully placed with the taxpayer for legal adoption by the taxpayer, shall be treated as a child of such individual by blood.