On a deceased's birthday, this condolence letter can be sent to their family and friends.
Dear {Recipient},
I'm writing this note because, as we approach {Deceased}'s birthday, I've been thinking about you a lot and wishing you well. Although it's been {number} years, I want you to know that I am still here for you in any capacity you need from me.
I can't believe {Deceased} would have been {age} by now. It's hard not to think of all of the things {he/she} might have done over the last few years, but it gives me no small amount of joy to remember the way that {he/she} always {birthday tradition/wishes/anecdotes}.
My thoughts and prayers are with you today and every day.
Love,
{Sender}