Mr and Mrs = Familie
Monsieur and madame.
Mr- and Mrs- Iyer - 2002 is rated/received certificates of: Germany:12 (DVD) UK:15
Mr and Mrs
Mr and Mrs is correct or Mrs and Mr is correct
Mr. and Mrs. (ex. "Hello, Mr. and Mrs. Evans" instead of "Hello, Mrs. and Mr. Evans")
Mr. & Mrs. Smith
"Frau", the German word equivalent of "Mrs." in English. Because "Herr" is Mr., his spouse would be Mrs.: Frau.
In the US it is normally Mr. and Mrs.
On an envelope as part of the address: Familie When referring to a couple: die ..... e.g. that's Mr and Mrs Bauer - das sind die Bauers das Ehepaar e.g. that's Mr and Mrs Bauer - das ist das Ehepaar Bauer
Dr. and Mrs. or Mr. and Dr.
I would address it to Mr and Mrs David Keys. For the salutation I would use Dear Mr and Mrs Keys.