Kidnapping an American Child in Another Country

My question involves criminal law for the state of: New York.

Twenty years ago an American toddler disappeared in a British park and was presumed drowned. Recently her parents discovered that she was alive and living in the United States with her assumed kidnappers. They also live here. They have reunited with their daughter who is now 21, but wonder if there is any criminal/legal recourse for them.

Thank you for your help!

Contact the British authorities to see if they are willing to press charges. The FBI and USCIS might get involved for the method used to bring the child into the US.