What'd be the more common equivalent to Tolkien's "the young perish and the old linger"?

The young perish and the old linger, withering.
^{The Two Towers by J.R.R. Tolkien}

Is there a common English phrase for when an old person, unfortunately, watches a young person die before them, even though the old one wishes it were the other way around?

For example, imagine a grandma watches her beloved grandchild die because of an incurable disease.

The young perish and the old linger, withering.

Some consider this to be a personal commentary on World War II

As you may recall, both of Tolkien's sons were combatants in the war. It seems that as a worried parent he was possibly making a personal comment about the unjust toll taken upon the youth of the world during war...so I will answer in the same vein with a qualification...

...Unless you are looking for a more common phrase as used in cases of fatalities from accident or child-hood disease...

"No parent should have to bury their child."

...which ironically also comes from Tolkien (King Theoden) and is more well-known.

...I am offering a few suggestions:

“War is young men dying and old men talking” -FDR

“I'm fed up to the ears with old men dreaming up wars for young men to die in.” -George McGovern

"Old soldiers never die, they just fade away" -General Douglas MacArthur

But for me, the most significant comment comes from a long forgotten poem...

If I were fierce, and bald, and short of breath, ...
I'd live with scarlet Majors at the Base,
And speed glum heroes up the line to death.
You'd see me with my puffy petulant face,
Guzzling and gulping in the best hotel,
Reading the Roll of Honour. "Poor young chap,"
I'd say—"I used to know his father well;
Yes, we've lost heavily in this last scrap."
And when the war is done and youth stone dead,
I'd toddle safely home and die—in bed.

Base Details by Siegfried Sasoon (1917)

All of that said, the original from Tolkien is almost poetry; and like most poetry it is wide-open for interpretation.

Is there a common English phrase for when an old person, unfortunately, watches a young person die before them, even though the old one wishes it were the other way around?

Reading all of the above, it appears that the answer is "No, there isn't."

There is nothing more than phrases, some common, some good, some bad that express the emotion of such an event.