No attorney for a claimant or plaintiff shall for the purpose of settlement or payment combine or group two or more claims or causes of action or judgments therefor on behalf of separate clients, and each such demand or action shall be settled or compromised independently upon its own merits and with regard to the individual interest of the client. No attorney for a defendant shall participate in the settlement of any such claims or actions on the basis directly or indirectly of combining or grouping claims or actions belonging to different persons.