Cruel agent upset family member (5-5)

I believe the answer is:

great-uncle

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'family member' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see a link between them that I don't see?

'cruel agent upset' is the wordplay.
'upset' indicates anagramming the letters.
'cruel'+'agent'='cruelagent'
'cruelagent' is an anagram of 'GREAT-UNCLE'.

Can you help me to learn more?

(Another definition for great-uncle that I've seen is " Relative".)

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