We're so happy to welcome you to the family! 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. An open letter to my future daughter in law. I knew when God gave me that precious little boy, the day would come when I would have to let him go. 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. Dear Daughterinlaw,. Today, you enter our home with new dreams and hope. Think of it as your organization's handshakea way to say, "We're thrilled you're here, and here's how to get the most out of your membership.".