Child Custody determination in family law is a herculean task. It typically depends on the balancing of interests between two parents that works in tandem with the best interest of the child. This paper addresses the legal and constitutional factors that affect custody adjudication in the 20th century such as feminist jurisprudence, and the growing concept of joint custody with primary caretaker rule. The paper also examines the role and impact of assisted reproductive technology on custody adjudication. Most importantly, the paper focuses on the best interest of the child doctrine under Article 3(1) of the United Nations Convention on the Rights of the Child and why national courts must interpret the standard in light of their cross-cultural differences. The paper also provides proposals for child custody arrangements across national borders for the 21st century.