We're so happy to welcome you to the family! You will always be the most important girl in Tyler's life which makes you very important to me.The day he proposed to you, you became 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. Here are 10 things your welcome letter or email to new members must include plus a template that can be customized for your organization. Letter to my new daughter in law. Discover Pinterest's best ideas and inspiration for Letter to my new daughter in law. 1. Enter the date at the top of the letter. Dear Daughterinlaw,.