In a divorce case, the court served a summons on the client's father, but the client's father could not contact the client. Is this summons valid? What is the legal basis?

According to legal practice, a summons is valid only if it is signed by an adult family member of the party concerned. However, if this adult family member can prove that it is really impossible to contact the party concerned, then the court will serve it in the form of an announcement after exhausting other means. After the expiration of the announcement, if the parties still do not appear, the court will regard it as served according to law and make a judgment in default on this basis.