@jodeej Did your transplant center give you examples of letters? I think that can be helpful. If not I would be happy to scan them in and put them out here. Also, my center recommended not writing immediately since the family's grief is so raw then, so it's probably best that he has not written yet.
Honestly, it was the most difficult thing I ever had to write in my life. How do you express extreme gratitude and sympathy all at the same letter? Not easy.
JK