Mr. and Mrs. Strauss, a wealthy couple traveling on the Titanic, responded to the unfolding disaster with composure. Mr. Strauss refused to leave his wife behind as the ship sank, insisting that they would stay together. They were last seen sitting on a deck chair, embracing each other, ultimately succumbing to the freezing waters. Their devotion to each other became one of the many poignant stories from that tragic night.
I believe she was already divorced from Mr. Brown nor that he was a passenger on the Titanic.
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")
Bravo Mr- Strauss - 1943 was released on: USA: 26 February 1943
Mr. Andrews had died on the Titanic voyage.
Mr. & Mrs. Smith
In the US it is normally Mr. and Mrs.
Dr. and Mrs. or Mr. and Dr.
Mr. Lucien Philip Smith and Mrs. Mary Eloise Smith (nee Hughes). They were both from Huntington West Virginia. Mrs. Smith Survived, her husband did not.
I would address it to Mr and Mrs David Keys. For the salutation I would use Dear Mr and Mrs Keys.
Mr. used to be acceptable to address a household by just using the last name, e.g. "Mr. Jones". In modern times, it is typically to use "Mr. and Mrs. Jones" or "Mr. and Mrs. Timothy Jones".