Take John Smith as a sample name. If you are sure he is married, your best option is
Mr. & Mrs. John Smith
If this is for a reunion-type event, and you are not sure if the alum is married:
Mr. John Smith & Guest
For an alum who is a woman, if you don't know her new last name, you might try
Ms. Jessica Smith & Spouse (or & Guest)
The Honorable Mr. James Jones and Mrs. Evelyn Jones
Say there last name was "Smith" you would write Mr. and Mrs. Smith.
A baronet is addressed as "Sir", and his wife as "Lady". Exactly how to address the envelope is a little dicey , but "Sir John Doe and Lady Doe" would be acceptable, I would think.
Dr. [Husband's Full Name] and Dr. [Wife's Full Name]
Mr. & Mrs. <lastname>
Addressing a husband and wife who are both Reverends: Reverends John & Jane Doe.
Dr. & Mrs. John Smith
Dr. Mary Smith and Mr. James Doe
if addressing an envelope it would be to the Reverend Canon or just Canon. His wife would be Mrs... The oral address would be Canon, and his wife Mrs.....
How about Mr. and Mrs.
Drs. _______ and ________ Smith
Type your answer here... Mr. and Mrs. Mark Henderson
Pastors George and Martha Maloney