This letter simply expresses joy and love to one of the other members of your family.
1234, Main Street
Boston, MA 02123
07 April, 2005
<Recipient Address Goes Here>
Because no one chooses their family, it's easy to take them for granted. And since I just don't get the opportunity often enough, I thought I'd take a moment to let you know how wonderful it is that we're related. You've always been there for me, no matter how daunting the task or inconvenient the request. I can't tell you how many times I've thought to myself, "What would I do without my family?"
I've always felt that we were more than just family; we're good friends, too. I just wanted you to know how much I love you and how glad I am that you're my <relationship>.
encl: <List of enclosed items goes here>