Oof. That got morbid quick.
I think that's a perfectly rational fear though; I wouldn't really count is as a phobia.
Phobia is broken down from the Greek word Phobos. Fear. It's defined as an "Irrational or extreme fear of something".
I've watched my grandfather die of a bone marrow disease before my eyes, three other family members have left me since then. Other than them, one of my brother's closest friends, aged 20, died a room away from me (no foul play), then a friend's father passed due to cancer. Near bout a year ago, one of my closest friends, a man I would call my brother, was diagnosed with cancer. He was 18, same age as I am.
So yeah, I've been to too many funerals for my liking. And I worry constantly for those I still have. Sorry for the morbidity.