In 1989, governments across the world promised all children the same rights by adopting the UN Convention on the Rights of the Child. The Convention says what countries must do so that all children grow as healthy as possible, can learn at school, are protected, have their views listened to, and are treated fairly.
Article 9
Children must not be separated from their parents unless it is in their best interests (for example, if a parent is hurting a child).
Children whose parents have separated have the right to stay in contact with both parents, unless this might hurt the child.
http://www.unicef.org.uk/Documents/Publications/Child_friendly_CRC_summary_final.pdf