"A wife who loses a husband is called a widow. A husband who loses a wife is called a widower. A child who loses his parents is called an orphan. But...there is no word for a parent who loses a child, that's how awful and unimagible the loss is!"
Says a lot.
I think that is because you can never stop being a parent, even if you are a bereft one, which is the saddest part (not to put down the other forms of losses in the quote, of course).
"Making the decision to have a child is momentous. It is to decide forever to have your heart go walking around outside your body."
- Elizabeth Stone
Then what do you do when that heart stops walking around?