If you are more personally acquainted, "Dear Mary and John,"
Never separate the man's first and last names - in other words, do not write the couple as "John and Mary Jones," only as "Mary and John Jones."
You would use the first name of the husband and the first name of the wife. This is how you address a Japanese married couple through a letter.
You can address a letter to two doctors as: Drs. John & Jane Doe.
No, it should be Mr. & Mrs. John Doe. You only use 'Ms.' if you are addressing a letter to someone you do not know is married or single or; in these modern times some women prefer you address them as Ms.
In correspondence, addressing a married couple is : " Mr and Mrs John Smith " - the first name of the husband is the only one used. It is incorrect to address a letter to a married woman as " Mrs. Mary Smith. " A married woman traditionally takes the name of her husband and so a letter to her would properly read, " Mrs. John Smith." Surreyfan
Frau
When addressing a letter to a married couple where the husband is a Jr., you would write: Mr. John Doe Jr. and Mrs. Jane Doe. The Jr. suffix is included after the husband's name to indicate that he is the son with the same name as his father. It is important to use both spouses' names in the salutation to ensure both individuals are properly acknowledged.
You can address it to Mr and Mrs. Smith. You could address it is as the Smith Family. Or you could address it as Mr. Smith and Family.
You can address a letter Dear Fred and Bertha (or whatever the actual names are). Personally, I often address my letter Dear Folks. That way there won't be any dispute about why I put Fred's name before Bertha's.
Unfortauntely, we don't know the address of your land lady. However, If you're trying to address a letter to your land lady you'd just address her as Ms. or Mrs. depending on if she married or not.
By their first names, if it's informal. Otherwise Dear Mr ...... and Mrs/Miss/Ms .........
You can address them as 'Sir' if they are a man, ' Miss' if you do not know if the lady is married or not, 'Madam' if you know the lady is married. If you are writing a letter, and you do not know the gender, you can address him/her as 'Dear Sir/Madam'. If you do not want to use any of the above, you may use 'excuse me'. Hope this answers your question :)
You address the letter to the couple like if they're names are Robert and susy Henderson then you can write Mr. and Mrs. Robert Henderson and family :) That's what i did for my brother's graduation cards