Distance? I only have young, pre-teen kids, but based on my own relationships with my parents, the closeness we once had has shifted to my "new" immediate family. I expect there will come a time with my own kids where we're just not as "close" as we once were. I wonder if that has any impact on how some people process grief (it seemed to, from witnessing aunts/uncles who died before my grandparents, and how they processed it).

I can also add that a lot of my anxiety around the sudden loss of the child is the thought of their life being cut short. Everything that they could have experienced, all the potential -- gone. Sure, when you're in your 60's you still have lots of life left to live, but the weight of life being "cut too short" just doesn't seem like it'd feel as heavy as say, the death of a child, teen, or a young adult in their early 20's.

Knowledge that they weren't taken as a child, that they got to experience a fuller life.