Addressing wedding invitations can be a challenging task, but there is a proper protocol to follow. The Emily Post Institute, as well as several other etiquette sites and gurus, offer address templates to fit just about any wedding guest combination. You simply personalise the templates. Have extra envelopes on hand in case you misspell a name or make a mistake with your script, if addressing the invitations yourself.
Address the married parents of a bride or groom with full names and titles. An example from the Emily Post Institute: "Mr. John Kelly and Ms. Jane Kelly." If one of the parents is a doctor, address the doctor first, as in: "Dr. Jane Kelly and Mr. John Kelly." If both parents are doctors, then try: "The Doctors Kelly," "Drs. Jane and John Kelly / Drs. John and Jane Kelly," or "Dr. John Kelly and Dr. Jane Kelly / Dr. Jane Kelly and Dr. John Kelly," according to the Emily Post Institute.
Modify the address slightly if the parents are unmarried but living together. The two names should be written on separate lines, and you may begin with either name. An example from the Emily Post Institute is the following: Mr. John Kelly Ms. Jane Johnson
Address an envelope with only one name if the parents are divorced. You may need to find out which title the woman prefers. For example, it is appropriate to address a divorced woman with her married or maiden name. "Mrs. Jane Kelly," "Ms. Jane Kelly," or "Ms. Jane Johnson" are examples, according to the Emily Post Institute.