Uncle, but not of Romulus (5)

I believe the answer is:

remus

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'uncle' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for remus that I've seen before include "Co-founder of Rome" , "twin brother" , "Suckled by a she-wolf, I was" , "Brother to fifty two across" , "One of the founders of Rome" .)

I've seen this clue in the Evening Standard.

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