This is just hard to read.
My dad lost his sister in her early 50's of brain cancer - and unfortunately, she became psychotic during it, and rejected treatments as a result. No way we could've predicted it - she was in good health up until that point. A few months and my dad will hit the same age - in good shape (with some back problems - it's now my job to crawl under the house to run sprinkler wires for him), and hopefully it'll stay that way.
For now, I'm mostly worried about my grandparents - Grandpa (dad's side) is in the early stages of dementia. And who knows how many life stories he has yet to tell us? On mom's side, we lost her dad several years back of pancreatic cancer (hard to watch him getting weak, but he had his mind to the very end). We could've lost her mom (in her 70's) to breast cancer as well, at around the same time. But fortunately, she caught the lumps early enough, got it treated, and she's now in her late 80's and still doing well (albeit driving my mom a bit crazy, which then passes onto me). Getting up there in age though.