Forcibly taking a child by the biological father before divorce to dispute custody is not illegal, it is aggressive and the method is inappropriate. However, if a fight occurs during the taking, it may be illegal.
　　1. Before divorce, it is a matter of disputing child custody and can be resolved through negotiation between both spouses or by agreement divorce. If both parties disagree, they can file for divorce litigation with the local court regarding custody issues.

　　 2. After divorce, if the child is awarded to the mother, then the mother is the child's legal guardian. If the father wants to see the child, he should notify the mother and then pick up the child. If he takes the child without the mother's consent or forcibly takes the child away, it is illegal, and the mother can report to the police and hold him responsible.
　　Custody refers to the parents' personal rights over their children. There are custody rights for children born within marriage and outside marriage. In real life, due to various reasons, the custody rights of parents over their children may not be well protected.
Divorce generally results in one spouse losing custody rights. The losing party will lose the right to live with the child. However, the party who loses custody still has visitation rights and can regularly visit the child for relatively short periods as agreed or judged. Custody during divorce can be agreed upon by both parties; if not, the court must decide.
The court's custody judgment is generally based on the principle of benefiting the child's growth: mainly considering factors such as both spouses' education, work, income, age, family environment, and the child's age.