Abduction

Abduction is the criminal act of taking a person away by means of fraud, persuasion, by threat of violence or by force. Kidnapping, by comparison, is limited to a threat of violence or forcefully taking adults or by the taking of children. It often involves some form of false imprisonment. In some states, kidnapping and abduction are treated as the same thing. But in most jurisdictions they are separate crimes. Unlawful interference with family members such as removing a child from its parents is abduction. It does not matter if the minor consents or not. Kidnapping is the unlawful taking of a person against their will. Abduction can also mean the taking of any female person for the purposes of prostitution, concubinage or (forced) marriage.
Child abduction.
During wars, children are often abducted. They may be treated brutally or killed. They may be victims of sexual violence or may be used as soldiers. Children are abducted both by armed parties or governments. They may be taken as an act of retaliation against a population. 
International child abduction.
When a marriage breaks down, it is not uncommon for one parent to wish to return, with his or her children, to their state of origin. This is usually without the permission of the other parent. This becomes an international child abduction. The United Nations Convention on the Rights of the Child requires "State Parties shall take measures to combat the illicit transfer and non-return of children abroad". Also that they "promote the conclusion of bilateral or multilateral agreements or accession to existing agreements". International child abductions are a matter treated by civil law and in some cases criminal law.