A person who is generaly young (aged 27 to 37) that through many years of drinking and smoking, looks 15 to 25 years older.
Look at wendy, shes 32 and she looks 54! ewwwwwwwwwwwwwwwwwwwww is she young old
by brett calvin October 1, 2006
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Used to define a young person who is very mature in many ways
Michael is such a "young old man" he never sneaks out
by Bigbadadonis February 26, 2018
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old boy In Kempston, just as people say 'old man' as a term for their father, we also use 'old boy' to refer to our elder brothers. In the same way, 'young old boy' is used to refer to our younger brothers. This appears to be contained within Kempston and is dying out.

Half-brothers and step-borthers are also sometimes described in this way.

It is mostly only used in the genetic sense but is seldom used in terms of emotional bonds.
Excerpt
Person A: Aren't you somebody's little brother?
(person's B's response here)
Kempstonian person: Yeh, they're my young old boy.
by Walking Talking Dictionary August 10, 2006
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