Claiming a foster child, what to put for "legal parents"

We had a foster child placed with us by a qualifying agency, who lived with us for the full year. He qualifies as a dependent, but I'm stuck on the question of who his legal parents are under "add a dependent." I enter his info (birthdate, name, etc), choose that he's "my son" and the next thing it asks is who the legal parents are: myself, my husband, or both of us. Technically he's a ward of the state and we are not his legal parents. Later on that page, it allows me to select foster child and to answer related questions. I can't skip why the legal parents are and there are no other options. Do we just put that we are his legal parents?