A family genealogist discovered that his grandparent who was believed to have had six siblings actually had two more who had died very young; one died a few days after birth. The firstborn died at the age of one year old. My cousin referred to this firstborn as "the eldest". I found it jarring to hear someone who died at the age of one called "the eldest". Is that normal usage and am I out of line? Or does "eldest" actually mean that one has reached an age greater than the others in his/her group?
I checked the Wordnik page, which said:
from the GNU version of the Collaborative International Dictionary of English
adj. Oldest; longest in duration
adj. Born or living first, or before the others, as a son, daughter, brother, etc.; first in origin
from The Century Dictionary and Cyclopedia
Oldest; most advanced in age; that was born first: as, the eldest son or daughter.
from WordNet 3.0 Copyright 2006 by Princeton University
n. the offspring who came first in the order of birth
adj. first in order of birth
So, evidently, there's some precedent for the word being used either way.
I also found this interesting usage in a 2002 biography:
I hardly remembered Rolland, either. He was the eldest but died when he was twenty-two, a couple of years after his mother's death. I was a grown woman, with children of my own...
Source: Moving Out: A Nebraska Woman's Life by Polly Spence, 2002