Legal Question in Family Law in Arizona

It depends on the lawyer's role. Sometimes a lawyer serves as a neutral "mediator" meaning that they help to facilitate the divorce, but they do not give legal advice to either party. Sometimes a lawyer represents one party, but then communicates cooperatively with the other (unrepresented) party. There is not an appropriate situation in which one lawyer actually represents/advises both parties to a divorce. If this has occurred, it might be an ethical violation, but it doesn't invalidate the divorce - if either party believes there was legal misconduct that affected the terms of the divorce, then that party can ask the court to set aside the divorce and if the judge grants it, the issues could be re-negotiated/relitigated; however, this would be extremely unusual.