A child who is not the employee's natural child, stepchild, grandchild, or stepgrandchild, and who is adopted by the employee after the employee could become entitled to an old age or disability benefit under the Social Security Act (treating his or her railroad compensation as wages under that Act), is considered dependent on the employee during the employee's lifetime only if the requirements in paragraphs (a) and (b), and either (c) or (d) of this section are met:

(a) The child is adopted in the United States;

(b) The child began living with the employee before the child attained age 18;

(c) The child is living with the employee in the United States and received at least one-half of his or her support from the employee for the year before the month in which—

(1) The employee could become entitled to a social security benefit as described above; or

(2) The employee becomes entitled to a period of disability which continues until he or she could become entitled to a social security benefit as described above.

(d) In the case of a child born within the one-year period stated in paragraph (c) of this section, at the close of such period the child must have been living with and have been receiving at least one-half of his or her support from the employee for substantially all of the period that began on the date the child was born.

(e) “Substantially all” means—

(1) The child was living with and receiving one-half support from the employee when the employee could have become entitled to a social security benefit as described above; and

(2) Any period during which the child was not living with or receiving one-half support from the employee is not more than one-half the period from the child's birth to the employee's date of entitlement or three months, whichever is less.