It depends. If the stepchild and the stepparents have formed a support relationship, the stepchild shall bear the support obligation after the stepparents are old. If the stepson doesn't bear it, the old man can sue the stepson to bear the maintenance obligation and ask for alimony. Article 26 of the Civil Code stipulates that parents have the obligation to raise, educate and protect their minor children. Adult children have the obligation to support, help and protect their parents. Article 1067 If parents fail to perform their maintenance obligations, minor children or adult children who cannot live independently shall have the right to ask their parents to pay alimony. Parents who fail to perform their maintenance obligations, lack the ability to work or have difficulties in living have the right to claim alimony from their adult children. Article 14 of the Law on the Protection of the Rights and Interests of the Elderly shall fulfill the obligations of financial support, life care, spiritual comfort and special needs care for the elderly. Supporters refer to the children of the elderly and other people who have the obligation to support according to law. The spouse of the supporter shall assist the supporter in fulfilling his maintenance obligations.