You have a typo in the question header.
I think it is generally accepted that 18 or so is a good cutoff, if the person was not married and had no children -- although I think I have gone as high as 20. I think it should be case by case from age 14 and upwards, but that's me.
-
I have a young fellow who birth record says he was born in 1901, his death record says he died in 1917, but his military records claim he was 18 on enlistment (he was 15), and killed in action aged 19 years (he was 16). By most standards he Died Young - but he was also a military "veteran", so should he get a {{Died Young}} sticker and child mortality category, or just "veteran recognition"?