If you really, really, need to find someone - then you have to be willing to do your limited share of work as well. Even the most complex of names might have between two and five duplicate references. This includes information from any or all of the following resources. If a birth certificate is not available, any information that would normally appear on such a record and that you're aware of could be extremely important. Dentists maintain dental records.
Hospitals maintain medical records.
You might be surprised at information that you can uncover about someone from their own notebooks, books of entertainment, diaries, desk drawers, closets, under bed mattresses, and so on. Especially if they have no desire to be found, as in the case of many runaways. Just about every person on this planet has a secret that they keep from their parents, children, or spouse.