You need to get as much geographical info. as possible on the home's location, name, number, etc. Was this a state run or licensed home or was it a religious affiliated home? Any employee's name you know or can ferret out from family members who may have had a hand in helping your parents place the child would be very helpful
The laws and administrative rules for searching for/identifying children placed with state created/run homes may vary widely and be quite different from the rules internally created in a religious/church-based children's home. A search for him in either will have its own advantages and challenges.
For a state run home, definitely ask to see their rules in writing when it comes to family searches and reunions. This should be public information and you should have no problem accessing this, even though we're in different countries.