I apologize for butchering her name, but Agneiska Holland (of Europa,
Europa and The Secret Garden) directed a film between those two called
OLIVIER, OLIVIER.
It's about a rural French family whose son has disappeared for ten years
and then "returns" as a bisexual teenage boy who has been living on the
streets of Paris. The film deals with the family's initial relief then
reconciliation with this stranger, who may or may not be their long-lost
son.
It's not exactly adoption, but it's a fascinating family portrait.