1. A man who is the biological father of a child, as opposed to an adoptive or stepfather
The natural father has the right to seek custody of his child.
O pai biológico tem o direito de buscar a guarda de seu filho.
2. A man who has fathered a child, regardless of legal marital status or involvement in child-rearing
She decided to contact the natural father after many years of separation.
Ela decidiu entrar em contato com o pai biológico depois de muitos anos de separação.