Per the answer to Are children adopted by Jews Jewish? a child that is adopted by Jewish parents when they reach adulthood (13/12) are given the choice of remaining Jewish.
If I know of a child that is adopted and has not yet reached adulthood - perhaps this child will still choose to live as a gentile when they reach adulthood (13/12) - would this retroactively make wine seen by such a child into Yayin Nesech? (sources)