We're so happy to welcome you to the family! A "thank you for joining" membership letter should include a personalized greeting to the new member.Use the member's first name in your salutation. I wanted to share an open letter to my future daughter in law. Here are 10 things your welcome letter or email to new members must include plus a template that can be customized for your organization. Do you want new ways to welcome members into your church? Check out these top church membership welcome letter templates and best practices. Write a personalized "Letter to Our Future Son-In-Law" to welcome him to your family. Here's points you'll want to share with your new son. 1. Enter the date at the top of the letter.