Robert Cuffee, now deceased, lived with Belmira Lucas during the years 1948 through 1966. They were never married. They had two children: Ruby M. Lucas, in 1953, and Darin E. Lucas, in 1960. In 1966 Cuffee and Lucas separated. Cuffee died in 1968. He died without ever having acknowledged in writing his paternity of either Ruby or Darin, and it was never determined in any judicial proceeding during his lifetime that he was the father of either child. After Cuffee's death, Mrs. Lucas filed an application on behalf of Ruby and Darin for surviving children's benefits under 202 (d) (1) of the Social Security Act. Under the Act, certain children are relieved of the burden of such individualized proof of dependency. A child who is legitimate, or a child who would be entitled to inherit personal property from the insured parent's estate under the applicable state intestacy law, is considered to have been dependent at the time of the parent's death. A child is entitled to a presumption of dependency if the decedent, before death, (a) had gone through a marriage ceremony with the other parent, resulting in a purported marriage between them which, but for a nonobvious legal defect, would have been valid, or (b) in writing had acknowledged the child to be his, or (c) had been decreed by a court to be the child's father, or (d) had been ordered by a court to support the child because the child was his. Social Security determined the children had failed to demonstrate their dependency by proof that Cuffee either lived with them or was contributing to their support at the time of his death, or by any of the statutory presumptions of dependency, and thus that they were not entitled to survivorship benefits under the Act. This was affirmed on administrative appeal. Lucas (P) then filed this action, for review of the Secretary's decision. The District Court ultimately affirmed each of the factual findings of the administrative agency. P urged that denial of benefits in this case, where paternity was clear, violated the Fifth Amendment's Due Process Clause, as that provision comprehends the principle of equal protection of the laws, because other children, including all legitimate children, are statutorily entitled, as P's children are not, to survivorship benefits regardless of actual dependency. The District Court ruled that the statutory classifications were constitutionally impermissible. D appealed directly to the Supreme Court.