While the letter-writing format is best suited for presenting a message from a single person, there are times when joint written communication is required, such as letters from couples. When writing a letter from two people, you want to make sure that the letter's content and wording is truly a joint effort and an equal representation of both people's thoughts. To write a letter that truly comes from both of you, plan out your letter-writing process and communicate during the writing.
Plan the letter together. Discuss the outline before you start to write. Mention everything you want the letter to say and in what order. This way, whoever ends up doing the bulk of the drafting, the letter will contain sentiments or messages approved by both of you.
Sit down together during the writing. That way it's less likely that one of you will dominate the choices about what's said, include something the other didn't want or fail to include something the other did want.
Write line by line. Have the writer/typist read back the letter as it's being written for the other person's consideration so both agree on what's getting put down.
Switch off the person writing, either by alternating paragraphs, switching out halfway through or deciding beforehand which sections you each want to write.
Use proper pronouns for a joint letter. Write in the first person plural, using "we" and "us." If part of the letter needs to refer to just one of you or is something that only one of you wants to express, refer to that person in the third person by name.
Sign both names at the bottom.