Even though a profile has unknown biological parents (explicit pair), the adoptive parent relationships are used to calculate blood-related family and ancestors.
In this example: http://www.geni.com/people/Sydney-J-Rosenfeld-Steiner-Mikhail-Strabo/6000000036998021632 , the adoptive parents were added to Geni prior to adding the (unknown) biological parents.
This also affects reporting of (text describing) adoptive siblings as brothers & half-brothers, when there is no biological connection.