Legal analysis: When the biological mother divorces her stepfather, the custody of the child generally belongs to the mother, but if the stepfather and the child have formed a custody obligation relationship, the stepfather can ask for custody of the child. That is, after the biological mother remarried, she agreed with her stepfather to raise the children by herself. The stepfather failed to fulfill the obligation of educating and raising the children, and the custody of the children could only be owned by the biological mother. However, if the stepfather has educated and raised the child in his daily life without seriously damaging the child's rights or using violence, he has the right to fight for the custody of the child.

Legal basis: Civil Code of People's Republic of China (PRC).

Article 1084 The relationship between parents and children shall not be destroyed by the divorce of parents. After the divorce, the child is still the child of both parents, whether or not the parents directly raise him. After divorce, parents still have the right and obligation to raise, educate and protect their children. After divorce, children under two years old are directly raised by their mothers. For a child who has reached the age of two, if both parents fail to reach an agreement on the issue of support, the people's court shall make a judgment based on the specific circumstances of both parties and the principle of being most beneficial to the minor children. Children over the age of eight should respect their true wishes.

Article 1085 If a child is directly raised by one party after divorce, the other party shall bear part or all of the alimony. The amount and duration of the expenses shall be agreed upon by both parties; If the agreement fails, the people's court shall make a judgment.

Article 1072 Stepparents and stepchildren shall not be abused or discriminated against. The provisions of this law on the relationship between parents and children shall apply to the rights and obligations between stepfathers or stepmothers and their stepchildren.