Based on what I read, I do not think the DNA will be of the bio relatives unless someone went inside that we didn't hear about. (coloring by me)
CODIS and NDIS Fact Sheet — FBI
45. What are the requirements for the collection of Family Reference Samples for entry and searching in NDIS?
Relatives of a missing person must be willing to provide a DNA sample and
sign a consent form in the presence of law enforcement. Only DNA samples collected voluntarily from relatives of a missing person are eligible for searching in NDIS. Those profiles will be used only for identifying a missing person or remains. (34 U.S.C. § 12592(a)(4)).
Law enforcement personnel must witness the voluntary collection of the Family Reference Samples and a consent and information form must be completed and signed by the person providing the DNA sample. The identity of the contributor providing the DNA sample must be verified by law enforcement (e.g., through presentation of an appropriate government-issued identification card). Family reference samples which are not submitted by law enforcement and with the appropriate documentation will not be accepted for entry into NDIS.