oh yes of course. Look at online and you can see many sites that you pay to get information on others. a good, honest PI would judge the case and decide whether or not to participate. In this case - I think it's perfectly ethical and moral. Obviously - a good, honest PI would refuse to accept the request to gather info on someone if he senses some stalking going on.
You simply need to supply your BF with any information you have. the names of your adoptive parents, date of adoption, name of adoption agency, birth place, etc. Everything's on record (unless the record building was burnt down or flooded).
good luck! 
