McCarthy's longtime client Arnold Munson and his son Donald have been sued jointly for an automobile accident involving Donald. McCarthy has been representing Donald and the pleadings have now been amended to include Arnold. McCarthy can represent both defendants if he obtains informed consent in writing from both. They must understand the risks of sharing confidential information and limiting certain defenses, as well as the lawyer's conflicting duties of loyalty. So long as both consent is obtained, joint representation would not violate the Rules of Professional Conduct for this lawsuit.